Restricted stock granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Document Type Document Type Other (expense) income, net Other Nonoperating Income (Expense) Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Related Party [Axis] Related Party [Axis] Treasury Stock Treasury Stock [Member] Accounts payable and other accrued expenses Increase (Decrease) in Accounts Payable and Accrued Liabilities Payables and Accruals [Abstract] Payables and Accruals [Abstract] Employee Benefit Plans Retirement Benefits [Text Block] Intelligence Clients Intelligence Clients [Member] Intelligence Clients [Member] Schedule of accumulated other comprehensive loss Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] Level 3 Fair Value, Inputs, Level 3 [Member] Guarantor Obligations, Nature [Domain] Guarantor Obligations, Nature [Domain] Debt issuance costs Debt Issuance Costs, Gross Statistical Measurement [Domain] Statistical Measurement [Domain] LIABILITIES AND STOCKHOLDERS’ EQUITY Liabilities and Equity [Abstract] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Other long-term liabilities Increase (Decrease) in Other Noncurrent Liabilities Derivatives Derivative Instruments and Hedging Activities Disclosure [Text Block] Security Exchange Name Security Exchange Name Intangible assets, net of accumulated amortization Intangible Assets, Net (Excluding Goodwill) Other Interest Income (Expense), Other Interest Income (Expense), Other Contract assets: Contract with Customer, Asset, after Allowance for Credit Loss [Abstract] Proceeds from debt issuance Proceeds from Issuance of Long-term Debt Operating income Operating Income (Loss) Total current liabilities Liabilities, Current Summary of Contract Balances Contract with Customer, Contract Asset, Contract Liability, and Receivable [Table Text Block] Prepaid expenses and other current assets Prepaid Expense and Other Assets, Current Variable Rate [Domain] Variable Rate [Domain] Variable Rate [Axis] Variable Rate [Axis] Commitments and contingencies (Note 18) Commitments and Contingencies Repurchases of common stock Payments for Repurchase of Common Stock ASSETS Assets [Abstract] Entity Address, State or Province Entity Address, State or Province Cash paid for amounts included in the measurement of lease liabilities Operating Lease, Payments Earnings per common share Earnings Per Share Reconciliation [Abstract] Accumulated Other Comprehensive Loss Comprehensive Income (Loss) Note [Text Block] Accounts Payable and Other Accrued Expenses Accounts Payable and Accrued Liabilities Disclosure [Text Block] Retained earnings Retained Earnings (Accumulated Deficit) Operating lease right-of-use assets Operating Lease, Right-of-Use Asset Loss on debt extinguishment Loss on debt extinguishment Gain (Loss) on Extinguishment of Debt Undistributed earnings allocated to participating securities, diluted Undistributed Earnings (Loss) Allocated to Participating Securities, Diluted 2022 Lessee, Operating Lease, Liability, to be Paid, Year One Repurchase of common stock (shares) Repurchase of common stock (in shares) Treasury Stock, Shares, Acquired Stock options outstanding (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number 2025 Lessee, Operating Lease, Liability, to be Paid, Year Four Thereafter Lessee, Operating Lease, Liability, to be Paid, after Year Four Lessee, Operating Lease, Liability, to be Paid, after Year Four Unrecognized compensation cost related to unvested stock-based compensation agreements Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount Undistributed earnings allocated to participating securities, basic Undistributed Earnings (Loss) Allocated to Participating Securities, Basic AOCI Attributable to Parent, Net of Tax [Roll Forward] AOCI Attributable to Parent, Net of Tax [Roll Forward] Customer [Axis] Customer [Axis] Fair Value by Liability Class [Domain] Fair Value by Liability Class [Domain] Beginning balance (shares) Ending balance (shares) Shares, Outstanding Hedging Designation [Domain] Hedging Designation [Domain] Total operating lease costs Lease, Cost Net cash paid during the period for: Cash Payments Abstract Cash paid during the period for: Other comprehensive income (loss), net of tax: Other Comprehensive Income (Loss), Net of Tax [Abstract] Common stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Debt extinguishment costs Payment for Debt Extinguishment or Debt Prepayment Cost Other long-term liabilities Total other long-term liabilities Other Liabilities, Noncurrent Liability Class [Axis] Liability Class [Axis] Stock-based compensation expense APIC, Share-based Payment Arrangement, Increase for Cost Recognition Sub-contractor Sales Channel, Through Intermediary [Member] Redemption of original principal amount, redemption period (in days) Debt Instrument, Redemption of Aggregate Principal Amount, Redemption Period Debt Instrument, Redemption of Aggregate Principal Amount, Redemption Period Payments to related party Related Party Transaction, Amounts of Transaction Revenue Revenue from Contract with Customer, Excluding Assessed Tax Measurement Frequency [Domain] Measurement Frequency [Domain] Stock price on grant date (in dollars per share) Share Price Concentration risk, percentage Concentration Risk, Percentage Geographical [Domain] Geographical [Domain] Defined Benefit Plan Disclosure [Line Items] Defined Benefit Plan Disclosure [Line Items] Fair value of derivative liabilities Derivative Instruments in Hedges, Liabilities, at Fair Value Statement [Line Items] Statement [Line Items] Class of Stock [Domain] Class of Stock [Domain] Tax Period [Axis] Tax Period [Axis] Quarterly periodic payment percentage, principal Debt Instrument, Quarterly Periodic Payment Percentage, Principal Debt Instrument, Quarterly Periodic Payment Percentage, Principal Accounts Receivable, Net of Allowance Loans, Notes, Trade and Other Receivables Disclosure [Text Block] Derivative Instruments and Hedging Activities Disclosures [Line Items] Derivative Instruments and Hedging Activities Disclosures [Line Items] Contingent consideration, liability Business Combination, Contingent Consideration, Liability, Noncurrent Statement [Table] Statement [Table] Interest cost Defined Benefit Plan, Interest Cost Statistical Measurement [Axis] Statistical Measurement [Axis] Summary of Other Long-Term Liabilities Schedule of Other Assets and Other Liabilities [Table Text Block] Long term derivative instruments Derivative Liability, Noncurrent Retirement Plan Name [Domain] Retirement Plan Name [Domain] Entity Small Business Entity Small Business Derivative Instruments and Hedging Activities Disclosures [Table] Derivative Instruments and Hedging Activities Disclosures [Table] Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Other long-term assets Contract with Customer, Asset, after Allowance for Credit Loss, Noncurrent [Abstract] Fair Value, Measurements, Fair Value Hierarchy [Domain] Fair Value Hierarchy and NAV [Domain] Debt Debt Disclosure [Text Block] Long-term disability obligation Postemployment Benefits Liability, Noncurrent Proceeds from issuance of common stock Proceeds from Issuance of Common Stock September 1, 2023 Debt Instrument, Redemption, Period One [Member] Amendment Flag Amendment Flag Reconciliation of the income used to compute basic and diluted EPS Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Time-and-materials Time-and-materials Contract [Member] Revolving credit facility, amount outstanding Long-term Line of Credit Repayment of debt Repayments of Debt Amounts reclassified from accumulated other comprehensive loss Reclassification from AOCI, Current Period, Net of Tax, Attributable to Parent Net cash provided by operating activities Net Cash Provided by (Used in) Operating Activities Entity Central Index Key Entity Central Index Key Related Party [Domain] Related Party [Domain] Measurement Frequency [Axis] Measurement Frequency [Axis] Related Party Transaction [Line Items] Related Party Transaction [Line Items] Derivatives designated as cash flow hedges Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent [Member] Derivative Instrument [Axis] Derivative Instrument [Axis] Other Noncurrent Liabilities Other noncurrent liabilities Other Noncurrent Liabilities [Member] September 1, 2025 Debt Instrument, Redemption, Period Three [Member] Senior Notes Senior Notes [Member] Customer [Domain] Contract with Customer, Sales Channel [Domain] Geographical [Axis] Geographical [Axis] Tax (benefit) expense Reclassification from AOCI, Current Period, Tax Earnings for basic computations Undistributed Earnings, Basic Deferred payment on obligation interest Deferred Payment Obligation, Interest Payment Deferred Payment Obligation, Interest Payment Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Global Commercial Clients Global Commercial Clients [Member] Global Commercial Clients [Member] Dilutive stock options and restricted stock (in shares) Weighted Average Number Diluted Shares Outstanding Adjustment Income Statement Location [Axis] Income Statement Location [Axis] Allowance for doubtful accounts Accounts Receivable, Allowance for Credit Loss, Current Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Income Statement Location [Domain] Income Statement Location [Domain] 2023 Lessee, Operating Lease, Liability, to be Paid, Year Two Cash flows from financing activities Net Cash Provided by (Used in) Financing Activities [Abstract] Estimate of amount to be reclassified over the next 12 months Interest Rate Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months, Net Notional amount of interest rate swaps Derivative, Notional Amount Bonus Accrued Bonuses, Current Schedules of Lease Cost Lease, Cost [Table Text Block] 2024 Lessee, Operating Lease, Liability, to be Paid, Year Three Other long-term assets Other Assets, Noncurrent Plan Name [Axis] Plan Name [Axis] Officer Medical Plan Officer Medical Plan [Member] Officer Medical Plan [Member] Issuance of common stock Stock Issued During Period, Value, New Issues Concentration Risk [Table] Concentration Risk [Table] Total Liabilities Financial Liabilities Fair Value Disclosure Total assets Assets Related-Party Transactions Related Party Transactions Disclosure [Text Block] Current derivative instruments Derivative Liability, Current Interest expense on debt Interest Expense, Debt Title of 12(b) Security Title of 12(b) Security Contract with Customer, Basis of Pricing [Axis] Contract with Customer, Basis of Pricing [Axis] Antidilutive Securities [Axis] Antidilutive Securities [Axis] Contract liabilities: Contract with Customer, Liability [Abstract] Total Assets Other Assets, Fair Value Disclosure Cost of revenue Cost of Sales [Member] Number of directors Number of Directors Number of Directors Interest expense Total Interest Expense Interest Expense on Condensed Consolidated Statements of Operations Interest Expense Depreciation and amortization Depreciation, Depletion and Amortization Deferred compensation arrangement with individual, annual cash award granted per year of service, amount Deferred Compensation Arrangement with Individual, Annual Cash Award Granted per Year of Service, Amount Deferred Compensation Arrangement with Individual, Annual Cash Award Granted per Year of Service, Amount Total liabilities Liabilities Income tax uncertainty Liability for Uncertainty in Income Taxes, Noncurrent Unrecognized compensation cost, amortization period Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition Retirement Plan Type [Axis] Retirement Plan Type [Axis] Less: imputed interest Lessee, Operating Lease, Liability, Undiscounted Excess Amount Schedule of Related Party Transactions, by Related Party [Table] Schedule of Related Party Transactions, by Related Party [Table] Contract with customer, liability, revenue recognized Contract with Customer, Liability, Revenue Recognized Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Abstract] Level 1 Fair Value, Inputs, Level 1 [Member] Amount of Gain or (Loss) Recognized in AOCL on Derivatives Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification and Tax Fair Value, Recurring and Nonrecurring [Table] Fair Value, Recurring and Nonrecurring [Table] Total revenue (as a percent) Revenue From Contract With Customer, Excluding Assessed Tax, Percentage Revenue From Contract With Customer, Excluding Assessed Tax, Percentage Dividends paid (in dollars per share) Common Stock, Dividends, Per Share, Cash Paid Prime Contractor Sales Channel, Directly to Consumer [Member] Debt Instrument [Axis] Debt Instrument [Axis] Additional Paid-In Capital Additional Paid-in Capital [Member] Antidilutive Securities, Name [Domain] Antidilutive Securities, Name [Domain] Disaggregation of Revenue [Line Items] Disaggregation of Revenue [Line Items] Repurchase of common stock Repurchase of common stock, value Treasury Stock, Value, Acquired, Cost Method 2017 Senior Notes Senior Notes due 2025 Senior Notes Due 2025 [Member] Senior Notes Due 2025 [Member] Adjustments to reconcile net income to net cash provided by operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Litigation Case [Axis] Litigation Case [Axis] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis] Revenue from Contract with Customer [Abstract] Revenue from Contract with Customer [Abstract] Guarantor obligations, reduction to available borrowings Guarantor Obligations, Liquidation Proceeds, Monetary Amount Common stock, outstanding (in shares) Common Stock, Shares, Outstanding Income Tax Disclosure [Abstract] Income Tax Disclosure [Abstract] Variable lease cost Variable Lease, Cost Revolving Credit Facility Revolving Credit Facility [Member] Loss Contingency Nature [Axis] Loss Contingency Nature [Axis] Post-retirement Plans Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent [Member] Common stock, authorized (in shares) Common Stock, Shares Authorized Concentration Risk Type [Axis] Concentration Risk Type [Axis] Stock option exercises Proceeds from Stock Options Exercised Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items] Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items] Guarantor Obligations, Nature [Axis] Guarantor Obligations, Nature [Axis] Defined benefit plan, unfunded status of plan Defined Benefit Plan, Funded (Unfunded) Status of Plan Vacation Accrued Vacation, Current Accrued compensation and benefits Increase (Decrease) in Employee Related Liabilities Income Statement [Abstract] Income Statement [Abstract] Accumulated Other Comprehensive Income (Loss) Totals AOCI Attributable to Parent [Member] Losses on dispositions Gain (Loss) on Disposition of Assets Postretirement benefit obligations Liability, Pension and Other Postretirement and Postemployment Benefits, Noncurrent Operating lease liabilities, net of current portion Operating Lease, Liability, Noncurrent Prepaid expenses and other current assets Increase (Decrease) in Prepaid Expense and Other Assets Change in postretirement plan costs Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax Restricted stock, total fair value Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Fair Value Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Fair Value Interest payments Interest Paid, Including Capitalized Interest, Operating and Investing Activities Less: Unamortized debt issuance costs and discount on debt Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net Accounting Estimates Use of Estimates, Policy [Policy Text Block] Current assets: Assets, Current [Abstract] Comprehensive income Comprehensive Income (Loss), Net of Tax, Attributable to Parent Net secured leverage ratio Debt Instrument, Net Secured Leverage Ratio, Maximum Debt Instrument, Net Secured Leverage Ratio, Maximum Other comprehensive income (loss) before reclassifications OCI, before Reclassifications, Net of Tax, Attributable to Parent City Area Code City Area Code Schedule of accrued compensation and benefits Schedule of Accrued Compensation And Benefits [Table Text Block] Schedule of Accrued Compensation And Benefits [Table Text Block] Document Period End Date Document Period End Date Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] Provision for claimed indirect costs Liability for reductions and/or penalties from U.S Government audits Loss Contingency Accrual Remaining performance obligation, percentage Revenue, Remaining Performance Obligation, Percentage Other Long-Term Liabilities Other Liabilities Disclosure [Text Block] Schedule of Disaggregation of Revenue Disaggregation of Revenue [Table Text Block] Income before income taxes Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest Net income Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax Hedging Designation [Axis] Hedging Designation [Axis] Operating Loss Carryforwards [Table] Operating Loss Carryforwards [Table] Disaggregation of Revenue [Table] Disaggregation of Revenue [Table] Long-term Debt, Type [Domain] Long-term Debt, Type [Domain] Stock-based compensation expense Share-based Payment Arrangement, Noncash Expense Purchases of property, equipment, and software Payments to Acquire Productive Assets Other financing activities Proceeds from (Payments for) Other Financing Activities Designated as Hedging Instrument Designated as Hedging Instrument [Member] Senior Notes Senior Notes Due 2028 [Member] Senior Notes Due 2028 Cover [Abstract] Cover [Abstract] Base Rate Base Rate [Member] Term Loan A Tranche-A Loans [Member] Tranche A Loans [Member] Maximum eligible deferral of compensation, percentage Deferred Compensation Plans, Maximum Eligible Deferral of Compensation, Percentage Deferred Compensation Plans, Maximum Eligible Deferral of Compensation, Percentage Affiliated Entity Affiliated Entity [Member] Total Long-term Debt Contract with Customer, Sales Channel [Axis] Contract with Customer, Sales Channel [Axis] Leases Lessee, Operating Leases [Text Block] Fair Value Disclosures [Abstract] Fair Value Disclosures [Abstract] Unvested shares participating in the payment of the Company's dividends declared (in shares) Incremental Common Shares Attributable to Participating Nonvested Shares with Non-forfeitable Dividend Rights Retirement Plan Name [Axis] Retirement Plan Name [Axis] Service cost Defined Benefit Plan, Service Cost Cost of revenue Cost of Goods and Services Sold Share-based Payment Arrangement, Expensed and Capitalized, Amount [Table] Share-based Payment Arrangement, Expensed and Capitalized, Amount [Table] Schedule of Earnings Per Share, Basic, by Common Class, Including Two Class Method [Table] Schedule of Earnings Per Share, Basic, by Common Class, Including Two Class Method [Table] Total operating costs and expenses Costs and Expenses Equity Components [Axis] Equity Components [Axis] Change in unrealized gain (loss) on derivatives designated as cash flow hedges Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax Restricted stock Restricted Stock [Member] Share-based Payment Arrangement [Abstract] Share-based Payment Arrangement [Abstract] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Minimum Minimum [Member] Receivables [Abstract] Receivables [Abstract] Balance Sheet Location [Domain] Balance Sheet Location [Domain] Earnings for diluted computations Undistributed Earnings, Diluted Operating lease liabilities Operating Lease, Liability, Current Civil Clients Civil Clients [Member] Civil Clients [Member] Employer matching contribution, percent of match Defined Contribution Plan, Employer Matching Contribution, Percent of Match Long-term Accounts receivable–unbilled Contract with Customer, Asset, after Allowance for Credit Loss, Noncurrent Entity Interactive Data Current Entity Interactive Data Current Total postretirement medical expense Defined Benefit Plan, Net Periodic Benefit Cost (Credit) UNITED STATES UNITED STATES Fair Value Measurements Fair Value Disclosures [Text Block] Cash flows from operating activities Net Cash Provided by (Used in) Operating Activities [Abstract] Commitment fee percentage Line of Credit Facility, Commitment Fee Percentage Interest Rate Swap Interest Rate Swap [Member] Customer [Domain] Customer [Domain] Cumulative Effect, Period of Adoption, Adjustment [Member] Cumulative Effect, Period of Adoption, Adjustment [Member] Additional paid-in capital Additional Paid in Capital, Common Stock Entity Registrant Name Entity Registrant Name Stock options outstanding, unvested (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares Derivative [Table] Derivative [Table] Statement of Stockholders' Equity [Abstract] Statement of Stockholders' Equity [Abstract] Concentration Risk [Line Items] Concentration Risk [Line Items] Assets: Assets, Fair Value Disclosure [Abstract] Weighted average discount rate (as a percent) Operating Lease, Weighted Average Discount Rate, Percent Other Other Liabilities and Deferred Revenue, Noncurrent Redemption of original principal amount (as a percent) Debt Instrument, Redemption Price, Percentage Of Principal Amount Outstanding Debt Instrument, Redemption Price, Percentage Of Principal Amount Outstanding Number of reportable segments Number of Reportable Segments Schedule of Unrecognized Compensation Cost Share-based Payment Arrangement, Nonvested Award, Cost [Table Text Block] Retirement Plan Type [Domain] Retirement Plan Type [Domain] Noncash lease expense Noncash Lease Expense Noncash Lease Expense Interest rate Debt Instrument, Interest Rate, Effective Percentage Noncash financing activities Noncash Financing Activities Noncash Financing Activities Guarantor obligations, available amount Guarantor Obligations, Available Amount Guarantor Obligations, Available Amount Remaining performance obligation, expected timing, period two Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period Two Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period Two Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Accounts receivable, net of allowance Accounts receivable, net of allowance Accounts Receivable, after Allowance for Credit Loss, Current Total future lease payments Lessee, Operating Lease, Liability, to be Paid Depreciation and amortization Depreciation, Depletion and Amortization, Nonproduction EIP Amended and Restated Equity Incentive Plan [Member] Amended and Restated Equity Incentive Plan [Member] Debt Instrument, Redemption, Period [Domain] Debt Instrument, Redemption, Period [Domain] Tax Years 2016-2021 Tax Years 2016-2021 [Member] Tax Years 2016-2019 [Member] Operating Loss Carryforwards [Line Items] Operating Loss Carryforwards [Line Items] Retirement Liability, Pension and Other Postretirement and Postemployment Benefits, Current Entity Address, Postal Zip Code Entity Address, Postal Zip Code Deferred income taxes and income taxes receivable / payable Increase (Decrease) in Income Taxes September 1, 2024 Debt Instrument, Redemption, Period Two [Member] Accrued Compensation and Benefits Compensation Related Costs, General [Text Block] Goodwill Goodwill Total other comprehensive income (loss), net of tax Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent Long-term debt, maximum expanded loan facility Long-term Debt, Maximum Expanded Loan Facility Long-Term Debt, Maximum Expanded Loan Facility Document Transition Report Document Transition Report Debt Instrument, Redemption, Period [Axis] Debt Instrument, Redemption, Period [Axis] Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items] Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items] Remaining performance obligation, expected timing, period one Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period One Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period One Cost-reimbursable Cost Reimbursable Contract [Member] Cost Reimbursable Contract Face amount of debt Debt Instrument, Face Amount Level 2 Fair Value, Inputs, Level 2 [Member] Document Quarterly Report Document Quarterly Report Liabilities: Liabilities, Fair Value Disclosure [Abstract] General and administrative expenses General and Administrative Expense [Member] Equity [Abstract] Equity [Abstract] Annual Incentive Plan Annual Incentive Plan [Member] Annual Incentive Plan [Member] Vendor payables Accounts Payable, Trade, Current Accounting Standards Update [Extensible List] Accounting Standards Update [Extensible List] Cumulative Effect, Period of Adoption [Axis] Cumulative Effect, Period of Adoption [Axis] Derivative Contract [Domain] Derivative Contract [Domain] Weighted-average common shares outstanding for diluted computations (in shares) Weighted Average Number of Shares Outstanding, Diluted Revolver Revolver [Member] Revolver [Member] Litigation Case [Domain] Litigation Case [Domain] Schedule of Recurring Fair Value Measurements Fair Value Measurements, Recurring and Nonrecurring [Table Text Block] Letter of Credit Letter of Credit [Member] Basic (in dollars per share) Earnings Per Share, Basic Number of operating segments Number of Operating Segments Entity File Number Entity File Number Schedule of Accounts Payable and Accrued Liabilities Schedule of Accounts Payable and Accrued Liabilities [Table Text Block] Other Current Liabilities Other Current Liabilities [Member] Debt Disclosure [Abstract] Debt Disclosure [Abstract] Weighted average remaining lease term (in years) Operating Lease, Weighted Average Remaining Lease Term Supplemental Employee Retirement Plan Supplemental Employee Retirement Plan [Member] Billable expenses Billable Expenses Billable expenses include direct subcontractor expenses, travel expenses, and other expenses incurred to perform on contracts. Amortization of Debt Issuance Cost (DIC) and Original Issue Discount (OID) Amortization of Debt Issuance Costs and Discounts Net cash provided by financing activities Net Cash Provided by (Used in) Financing Activities Revenue, amount of remaining performance obligation Revenue, Remaining Performance Obligation, Amount Stock-based compensation expense Share-based Payment Arrangement, Expense Loss contingencies, number of plaintiffs Loss Contingency, Number of Plaintiffs Balance Sheet Location [Axis] Balance Sheet Location [Axis] Common stock, Class A — $0.01 par value — authorized, 600,000,000 shares; issued, 162,079,334 shares at September 30, 2020 and 161,333,973 shares at March 31, 2020; outstanding, 138,024,601 shares at September 30, 2020 and 138,719,921 shares at March 31, 2020 Common Stock, Value, Issued Premium payable (as a percent) Debt Instrument, Debt Covenant, Premium Payable, Percent Debt Instrument, Debt Covenant, Premium Payable, Percent Document Fiscal Year Focus Document Fiscal Year Focus Other comprehensive income (loss) before reclassifications, tax Other Comprehensive Income (Loss), Tax, Portion Attributable to Parent Current portion of long-term debt Less: Current portion of long-term debt Long-term Debt, Current Maturities Deferred compensation plan, assets Long term deferred compensation costs Deferred Compensation Plan Assets Schedule of Accounts Receivable, Net of Allowance Schedule of Accounts, Notes, Loans and Financing Receivable [Table Text Block] Entity Current Reporting Status Entity Current Reporting Status Retirement Benefits [Abstract] Retirement Benefits [Abstract] Term Loan B Tranche B Loans [Member] Tranche B Loans [Member] Related Party Transaction [Axis] Related Party Transaction [Axis] Other Liabilities Disclosure [Abstract] Other Liabilities Disclosure [Abstract] Schedule of Long-term Debt Instruments [Table] Schedule of Long-term Debt Instruments [Table] Long-term Debt, Current and Noncurrent [Abstract] Long-term Debt, Current and Noncurrent [Abstract] Current assets Contract with Customer, Asset, after Allowance for Credit Loss, Current [Abstract] Cash flows from investing activities Net Cash Provided by (Used in) Investing Activities [Abstract] Common stock, issued (in shares) Common Stock, Shares, Issued Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Schedule of Defined Benefit Plans Disclosures [Table] Schedule of Defined Benefit Plans Disclosures [Table] Total lease liabilities Operating Lease, Liability Amount of Gain or (Loss) Reclassified from AOCL into Income Interest Rate Cash Flow Hedge Gain (Loss) Reclassified to Earnings, Net Long-term debt, net of current portion Long-term Debt, Excluding Current Maturities Total accounts receivable, net Accounts Receivable, after Allowance for Credit Loss Contract with Customer, Basis of Pricing [Domain] Contract with Customer, Basis of Pricing [Domain] Redemption of aggregate principal amount (as a percent) Debt Instrument, Redemption Price, Percentage of Principal Amount Redeemed Defense Clients Defense Clients [Member] Defense Clients [Member] Accounts receivable, net of allowance Increase (Decrease) in Accounts Receivable Debt Instrument [Line Items] Debt Instrument [Line Items] Statement of Comprehensive Income [Abstract] Statement of Comprehensive Income [Abstract] Total stockholders’ equity Beginning of period End of period Stockholders' Equity Attributable to Parent Business Overview Nature of Operations [Text Block] Concentration Risk Type [Domain] Concentration Risk Type [Domain] Total liabilities and stockholders’ equity Liabilities and Equity Other Other Employee-related Liabilities, Current Loss Contingencies [Line Items] Loss Contingencies [Line Items] Accumulated other comprehensive loss Accumulated Other Comprehensive Income (Loss), Net of Tax Income Taxes Income Tax Disclosure [Text Block] Entity Address, City or Town Entity Address, City or Town Accrued compensation and benefits Total accrued compensation and benefits Employee-related Liabilities, Current Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Restricted stock units (RSUs) Restricted Stock Units (RSUs) [Member] Fixed-price Fixed-price Contract [Member] Operating lease cost Operating Lease, Cost Accounts payable and other accrued expenses Total accounts payable and other accrued expenses Accounts Payable and Accrued Liabilities, Current Hedging Relationship [Axis] Hedging Relationship [Axis] General and administrative expenses General and Administrative Expense Antidilutive options excluded from the computation of EPS (in shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Short-term lease cost Short-term Lease, Cost Equity Component [Domain] Equity Component [Domain] Reclassification out of Accumulated Other Comprehensive Income [Line Items] Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] Cash dividends paid Unvested shares, cash dividends paid Payments of Dividends Other long-term assets Increase (Decrease) in Other Noncurrent Assets Property and equipment, net of accumulated depreciation Property, Plant and Equipment, Net Entity Tax Identification Number Entity Tax Identification Number Deferred compensation plan, liabilities Long term deferred compensation plan liability Deferred Compensation Liability, Classified, Noncurrent Stock-Based Compensation Share-based Payment Arrangement [Text Block] Net income Net income Net Income (Loss) Attributable to Parent Changes in assets and liabilities: Increase (Decrease) in Operating Capital [Abstract] Interest Swap Expense Interest Expense, Debt, Interest Swap Interest Expense, Debt, Interest Swap Other current liabilities Other Liabilities, Current Remainder of 2021 Lessee, Operating Lease, Liability, to be Paid, Remainder of Fiscal Year London Interbank Offered Rate (LIBOR) London Interbank Offered Rate (LIBOR) [Member] Other comprehensive income (loss), net of tax Other Comprehensive Income (Loss), Net of Tax Leases [Abstract] Leases [Abstract] Percentage of consolidated EBITDA required for expansion of loan Debt Covenant, Expanded Loan, Percentage of Consolidated EBITDA Required Debt Covenant, Expanded Loan, Percentage of Consolidated EBITDA Required Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Total current assets Assets, Current Current Fiscal Year End Date Current Fiscal Year End Date Earnings per common share (Note 4): Earnings Per Share [Abstract] Earnings Per Share [Abstract] Compensation Related Costs [Abstract] Compensation Related Costs [Abstract] Post-retirement plans Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member] Stockholders’ equity: Stockholders' Equity Attributable to Parent [Abstract] Accumulated Other Comprehensive Income (Loss) [Line Items] Accumulated Other Comprehensive Income (Loss) [Line Items] Document Fiscal Period Focus Document Fiscal Period Focus Overnight Federal Funds Rate Overnight Federal Funds Rate [Member] Overnight Federal Funds Rate Number of employees Entity Number of Employees Operating lease liabilities Increase (Decrease) In Operating Lease Liabilities Increase (Decrease) In Operating Lease Liabilities Supplemental disclosures of cash flow information Supplemental Cash Flow Information [Abstract] Contracts with U.S. government agencies or other U.S. government contractors Government Contracts Concentration Risk [Member] Stock purchased by employees (in shares) Stock Issued During Period, Shares, Employee Stock Purchase Plans Redemption price (as a percent) Debt Instrument, Redemption Price, Percentage Financial Standby Letter of Credit Financial Standby Letter of Credit [Member] Entity Filer Category Entity Filer Category Summary of Stock-Based Compensation Expense Recognized in the Condensed Consolidated Statements of Operations Share-based Payment Arrangement, Expensed and Capitalized, Amount [Table Text Block] Income tax assessments Income Tax Examination, Estimate of Possible Loss Reclassification out of accumulated other comprehensive loss to net income Reclassification out of Accumulated Other Comprehensive Income [Table Text Block] Dividends paid per share of common stock Dividends, Cash Employees’ capital accumulation plan, total expense recognized Defined Contribution Plan, Cost Reclassification out of Accumulated Other Comprehensive Income [Table] Reclassification out of Accumulated Other Comprehensive Income [Table] Secured Debt Secured Debt [Member] Issuance of common stock (shares) Stock Issued During Period, Shares, New Issues United States District Court for the Eastern District of Virginia styled Langley v. Booz Allen Hamilton Holding Corp. United States District Court For The Eastern District Of Virginia Styled Langley V. Booz Allen Hamilton Holding Corp. [Member] United States District Court for the Eastern District of Virginia styled Langley v. Booz Allen Hamilton Holding Corp. [Member] Debt instrument, stated percentage Debt Instrument, Interest Rate, Stated Percentage Provision (benefit) for doubtful accounts Accounts Receivable, Credit Loss Expense (Reversal) Class A Common Stock Common Class A [Member] Current Accounts receivable–unbilled Contract with Customer, Asset, after Allowance for Credit Loss, Current Supplemental disclosures of non-cash investing and financing activities Noncash Investing and Financing Items [Abstract] Period for premium payable in connection with repricing transactions Debt Instrument, Debt Covenant, Premium Payable For Repricing Transactions, Term Debt Instrument, Debt Covenant, Premium Payable For Repricing Transactions, Term Stock options exercised (shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period Related Party Transactions [Abstract] Related Party Transactions [Abstract] Net increase in cash and cash equivalents Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect Hedging Relationship [Domain] Hedging Relationship [Domain] Schedule of Future Minimum Operating Lease Payments Lessee, Operating Lease, Liability, Maturity [Table Text Block] Loss Contingency, Nature [Domain] Loss Contingency, Nature [Domain] Recognition of liability related to future restricted stock units vesting Adjustments To Additional Paid In Capital Recognition Of Liability Related To Future Stock Option Exercises Adjustments To Additional Paid In Capital Recognition Of Liability Related To Future Stock Option Exercises Stock options Share-based Payment Arrangement, Option [Member] Weighted-average common shares outstanding for basic computations (in shares) Weighted Average Number of Shares Outstanding, Basic Long-term debt, basis spread on variable rate Debt Instrument, Basis Spread on Variable Rate Operating costs and expenses: Costs and Expenses [Abstract] Treasury stock (in shares) Treasury Stock, Shares Cash Flow Hedging Cash Flow Hedging [Member] Loss Contingencies [Table] Loss Contingencies [Table] Plan Name [Domain] Plan Name [Domain] Revenue Revenue from Contract with Customer [Text Block] Interest Interest Paid, Excluding Capitalized Interest, Operating Activities Tax Period [Domain] Tax Period [Domain] Payment of premium at redemption and write off of unamortized debt issuance costs Payment of Premiums and Write-Off of Debt Issuance Costs Payment of Premiums and Write-Off of Debt Issuance Costs Other current liabilities Increase (Decrease) in Other Current Liabilities Reserve for uncertain tax positions, acquisitions Liability For Uncertainty In Income Taxes, Noncurrent, Acquisitions Liability For Uncertainty In Income Taxes, Noncurrent, Acquisitions Operating lease liabilities arising from obtaining ROU assets Right-of-Use Asset Obtained in Exchange for Operating Lease Liability Basis of Presentation Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Class of Stock [Axis] Class of Stock [Axis] Schedule of Derivative Instruments Schedule of Derivative Instruments [Table Text Block] Income tax expense Income Tax Expense (Benefit) Tax Years 2013-2015 Tax Years 2013-2015 [Member] Tax Years 2013-2015 [Member] Income taxes Income Taxes Paid, Net Services Performed Under Subcontractor Services Performed Under Subcontractor [Member] Services Performed Under Subcontractor [Member] Cash and cash equivalents––beginning of period Cash and cash equivalents––end of period Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Employees’ capital accumulation plan, company-paid contributions Defined Contribution Plan, Employer Discretionary Contribution Amount Accrued expenses Accrued Liabilities, Current Diluted (in dollars per share) Earnings Per Share, Diluted Local Phone Number Local Phone Number Unfavorable Regulatory Action Unfavorable Regulatory Action [Member] Income before income taxes Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax Derivative Instruments and Hedging Activities Disclosure [Abstract] Derivative Instruments and Hedging Activities Disclosure [Abstract] Cumulative Effect, Period of Adoption [Domain] Cumulative Effect, Period of Adoption [Domain] Schedule of Debt Schedule of Debt [Table Text Block] Derivative [Line Items] Derivative [Line Items] Long-term debt outstanding Long-term Debt, Gross Entity Address, Address Line One Entity Address, Address Line One Advance payments, billings in excess of costs incurred and deferred revenue Contract with Customer, Liability Related Party Transaction [Domain] Related Party Transaction [Domain] Entity Emerging Growth Company Entity Emerging Growth Company Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table] Stock options exercised Stock Issued During Period, Value, Stock Options Exercised Prior to September 1, 2023 Debt Instrument, Redemption, Period Four [Member] Recognition of liability related to future restricted stock units vesting Adjustments To Additional Paid In Capital, Recognition Of Liability Related To Future Restricted Stock Units Vesting Adjustments To Additional Paid In Capital, Recognition Of Liability Related To Future Restricted Stock Units Vesting Revolving credit facility, maximum borrowing capacity Line of Credit Facility, Maximum Borrowing Capacity Award Type [Axis] Award Type [Axis] Maximum Maximum [Member] Amortization of debt issuance costs Amortization of Debt Issuance Costs Retained Earnings Retained Earnings [Member] Schedule of Interest Expense Interest Income and Interest Expense Disclosure [Table Text Block] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Components of net postretirement medical expense Schedule of Net Benefit Costs [Table Text Block] Effective income tax rate Effective Income Tax Rate Reconciliation, Percent Net cash used in investing activities Net Cash Provided by (Used in) Investing Activities Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Award Type [Domain] Award Type [Domain] Reserve for uncertain tax positions, research and development tax credits Liability For Uncertainty In Income Taxes, Noncurrent, Research And Development Tax Credits Liability For Uncertainty In Income Taxes, Noncurrent, Research And Development Tax Credits Guarantor obligations, carrying value Guarantor Obligations, Current Carrying Value Other Postretirement Benefits Plan Other Postretirement Benefits Plan [Member] Trading Symbol Trading Symbol Accumulated Other Comprehensive Income (Loss) [Table] Accumulated Other Comprehensive Income (Loss) [Table] Guarantor obligations, facility Guarantor Obligations, Facility Guarantor Obligations, Facility Treasury stock, at cost — 24,054,733 at September 30, 2020 and 22,614,052 shares at March 31, 2020 Treasury Stock, Value Total Contract with Customer, Asset, after Allowance for Credit Loss Earnings Per Share Earnings Per Share [Text Block] Organization, Consolidation and Presentation of Financial Statements [Abstract] Organization, Consolidation and Presentation of Financial Statements [Abstract] Current liabilities: Liabilities, Current [Abstract] Federal statutory rate (as a percent) Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent Entity Shell Company Entity Shell Company Accounts receivable–billed Billed Contracts Receivable Fair Value, Measurements, Recurring Fair Value, Recurring [Member] Proceeds from lines of credit Proceeds from Lines of Credit Recently Adopted Accounting Standards and Recent Accounting Pronouncements Not Yet Adopted New Accounting Pronouncements, Policy [Policy Text Block] Statement of Financial Position [Abstract] Statement of Financial Position [Abstract]