Retirement Benefits [Abstract] Employer matching contribution, percent of match Defined Contribution Plan, Employer Matching Contribution, Percent of Match Employees’ capital accumulation plan, total expense recognized Defined Contribution Plan, Cost Employees’ capital accumulation plan, company-paid contributions Defined Contribution Plan, Employer Discretionary Contribution Amount Schedule of Defined Benefit Plans Disclosures [Table] Schedule of Defined Benefit Plans Disclosures [Table] Retirement Plan Name [Axis] Retirement Plan Name [Axis] Retirement Plan Name [Domain] Retirement Plan Name [Domain] Officer Medical Plan Officer Medical Plan [Member] Officer Medical Plan [Member] Retirement Plan Type [Axis] Retirement Plan Type [Axis] Retirement Plan Type [Domain] Retirement Plan Type [Domain] Supplemental Employee Retirement Plan Supplemental Employee Retirement Plan [Member] Other Postretirement Benefits Plan Other Postretirement Benefits Plan [Member] Defined Benefit Plan Disclosure [Line Items] Defined Benefit Plan Disclosure [Line Items] 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 Service cost Defined Benefit Plan, Service Cost Interest cost Defined Benefit Plan, Interest Cost Net actuarial loss Defined Benefit Plan, Amortization of Gain (Loss) Total postretirement medical expense Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Defined benefit plan, unfunded status of plan Defined Benefit Plan, Funded (Unfunded) Status of Plan Maximum eligible deferral of compensation, percentage Deferred Compensation Plans, Maximum Eligible Deferral of Compensation, Percentage Deferred Compensation Plans, Maximum Eligible Deferral of Compensation, Percentage Deferred compensation plan, assets Deferred Compensation Plan Assets Deferred compensation plan, liabilities Deferred Compensation Liability, Classified, Noncurrent Debt Disclosure [Abstract] Schedule of Long-term Debt Instruments [Table] Schedule of Long-term Debt Instruments [Table] Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Long-term Debt, Type [Domain] Long-term Debt, Type [Domain] Secured Debt Secured Debt [Member] Revolving Credit Facility Revolving Credit Facility [Member] Senior Notes Senior Notes [Member] Debt Instrument [Axis] Debt Instrument [Axis] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Term Loan A Tranche-A Loans [Member] Tranche A Loans [Member] Term Loan B Tranche B Loans [Member] Tranche B Loans [Member] Debt Instrument [Line Items] Debt Instrument [Line Items] Interest expense on debt Interest Expense, Debt Deferred Payment Obligation Interest Deferred Payment Obligation, Interest Payment Deferred Payment Obligation, Interest Payment Amortization of Debt Issuance Cost (DIC) and Original Issue Discount (OID) Amortization of Debt Issuance Costs and Discounts Other Interest Expense, Other Total Interest Expense Interest Expense Commitments and Contingencies Disclosure [Abstract] Concentration Risk [Table] Concentration Risk [Table] Guarantor Obligations, Nature [Axis] Guarantor Obligations, Nature [Axis] Guarantor Obligations, Nature [Domain] Guarantor Obligations, Nature [Domain] Financial Standby Letter of Credit Financial Standby Letter of Credit [Member] Concentration Risk Type [Axis] Concentration Risk Type [Axis] Concentration Risk Type [Domain] Concentration Risk Type [Domain] Contracts with U.S. government agencies or other U.S. government contractors Government Contracts Concentration Risk [Member] Concentration Risk [Line Items] Concentration Risk [Line Items] Guarantor obligations, carrying value Guarantor Obligations, Current Carrying Value Guarantor obligations, reduction to available borrowings Guarantor Obligations, Liquidation Proceeds, Monetary Amount Guarantor obligations, facility Guarantor Obligations, Facility Guarantor Obligations, Facility Guarantor obligations, available amount Guarantor Obligations, Available Amount Guarantor Obligations, Available Amount Concentration risk, percentage Concentration Risk, Percentage Loss Contingencies [Table] Loss Contingencies [Table] Loss Contingency Nature [Axis] Loss Contingency Nature [Axis] Loss Contingency, Nature [Domain] Loss Contingency, Nature [Domain] Unfavorable Regulatory Action Unfavorable Regulatory Action [Member] Loss Contingencies [Line Items] Loss Contingencies [Line Items] Liability for reductions and/or penalties from U.S Government audits Loss Contingency Accrual Receivables [Abstract] Current assets Contract with Customer, Asset, Net, Current [Abstract] Accounts receivable–billed Billed Contracts Receivable Accounts receivable–unbilled Contract with Customer, Asset, Net, Current Allowance for doubtful accounts Allowance for Doubtful Accounts Receivable, Current Accounts receivable, net of allowance Accounts Receivable, Net, Current Other long-term assets Contract with Customer, Asset, Net, Noncurrent [Abstract] Accounts receivable–unbilled Contract with Customer, Asset, Net, Noncurrent Total accounts receivable, net Accounts Receivable, Net Provision for doubtful accounts Provision for Doubtful Accounts Earnings Per Share [Abstract] Schedule of Earnings Per Share, Basic, by Common Class, Including Two Class Method [Table] Schedule of Earnings Per Share Basic And Diluted by Common Class [Table] Schedule of Earnings Per Share Basic And Diluted by Common Class [Table] Class of Stock [Axis] Class of Stock [Axis] Class of Stock [Domain] Class of Stock [Domain] Class A Common Stock Common Class A [Member] Antidilutive Securities [Axis] Antidilutive Securities [Axis] Antidilutive Securities, Name [Domain] Antidilutive Securities, Name [Domain] Restricted stock Restricted Stock [Member] Stock options Employee Stock Option [Member] Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items] Schedule of Earnings Per Share Basic And Diluted by Common Class [Line Items] Schedule of Earnings Per Share Basic And Diluted by Common Class [Line Items] Earnings for basic computations Undistributed Earnings, Basic Weighted-average common shares outstanding for basic computations Weighted Average Number of Shares Outstanding, Basic Earnings for diluted computations Undistributed Earnings, Diluted Dilutive stock options and restricted stock (in shares) Weighted Average Number Diluted Shares Outstanding Adjustment Weighted-average common shares outstanding for diluted computations Weighted Average Number of Shares Outstanding, Diluted Earnings per common share Earnings Per Share Reconciliation [Abstract] Basic (in dollars per share) Earnings Per Share, Basic Diluted (in dollars per share) Earnings Per Share, Diluted Unvested shares participating in the payment of the Company's dividends declared Incremental Common Shares Attributable to Participating Nonvested Shares with Non-forfeitable Dividend Rights Unvested shares, cash dividends paid Payments of Dividends Undistributed earnings allocated to participating securities, basic Undistributed Earnings (Loss) Allocated to Participating Securities, Basic Undistributed earnings allocated to participating securities, diluted Undistributed Earnings (Loss) Allocated to Participating Securities, Diluted Antidilutive options excluded from the computation of EPS Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Equity [Abstract] Schedule of Common Stock Outstanding Schedule of Common Stock Outstanding Roll Forward [Table Text Block] Compensation Related Costs [Abstract] Bonus Accrued Bonuses, Current Retirement Liability, Pension and Other Postretirement and Postemployment Benefits, Current Vacation Accrued Vacation, Current Other Other Employee-related Liabilities, Current Total accrued compensation and benefits Employee-related Liabilities, Current Related Party Transactions [Abstract] Schedule of Related Party Transactions, by Related Party [Table] Schedule of Related Party Transactions, by Related Party [Table] Related Party [Axis] Related Party [Axis] Related Party [Domain] Related Party [Domain] Affiliated Entity Affiliated Entity [Member] Related Party Transaction [Axis] Related Party Transaction [Axis] Related Party Transaction [Domain] Related Party Transaction [Domain] Pledge Obligation Pledge Obligation [Member] Pledge Obligation [Member] Related Party Transaction [Line Items] Related Party Transaction [Line Items] Due to affiliate, current Due to Affiliate, Current Payment of pledge obligation Related Party Transaction, Amounts of Transaction Senior Notes Senior Notes Due 2025 [Member] Senior Notes Due 2025 [Member] Long-term Debt, Current and Noncurrent [Abstract] Long-term Debt, Current and Noncurrent [Abstract] Interest rate Debt Instrument, Interest Rate, Effective Percentage Long-term debt outstanding Long-term Debt, Gross Less: Unamortized debt issuance costs and discount on debt Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net Total Long-term Debt Less: Current portion of long-term debt Long-term Debt, Current Maturities Long-term debt, net of current portion Long-term Debt, Excluding Current Maturities Accounts Receivable, Net of Allowance Loans, Notes, Trade and Other Receivables Disclosure [Text Block] Disclosure of Compensation Related Costs, Share-based Payments [Abstract] Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table] Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table] Income Statement Location [Axis] Income Statement Location [Axis] Income Statement Location [Domain] Income Statement Location [Domain] Cost of revenue Cost of Sales [Member] General and administrative expenses General and Administrative Expense [Member] Award Type [Axis] Award Type [Axis] Award Type [Domain] Equity Award [Domain] Plan Name [Axis] Plan Name [Axis] Plan Name [Domain] Plan Name [Domain] EIP Amended and Restated Equity Incentive Plan [Member] Amended and Restated Equity Incentive Plan [Member] Annual Incentive Plan Annual Incentive Plan [Member] Annual Incentive Plan [Member] Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items] Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items] Stock-based compensation expense Allocated Share-based Compensation Expense Revenue from Contract with Customer [Abstract] Disaggregation of Revenue [Table] Disaggregation of Revenue [Table] Contract with Customer, Basis of Pricing [Axis] Contract with Customer, Basis of Pricing [Axis] Contract with Customer, Basis of Pricing [Domain] Contract with Customer, Basis of Pricing [Domain] Cost-reimbursable Cost Reimbursable Contract [Member] Cost Reimbursable Contract Time-and-materials Time-and-materials Contract [Member] Fixed-price Fixed-price Contract [Member] Customer [Axis] Customer [Axis] Customer [Domain] Customer [Domain] Defense Clients Defense Clients [Member] Defense Clients [Member] Intelligence Clients Intelligence Clients [Member] Intelligence Clients [Member] Civil Clients Civil Clients [Member] Civil Clients [Member] Global Commercial Clients Global Commercial Clients [Member] Global Commercial Clients [Member] Geographical [Axis] Geographical [Axis] Geographical [Domain] Geographical [Domain] UNITED STATES UNITED STATES Contract with Customer, Sales Channel [Axis] Contract with Customer, Sales Channel [Axis] Customer [Domain] Contract with Customer, Sales Channel [Domain] Prime Contractor Sales Channel, Directly to Consumer [Member] Sub-contractor Sales Channel, Through Intermediary [Member] Disaggregation of Revenue [Line Items] Disaggregation of Revenue [Line Items] Revenue Revenue from Contract with Customer, Excluding Assessed Tax Total revenue (as a percent) Revenue From Contract With Customer, Excluding Assessed Tax, Percentage Revenue From Contract With Customer, Excluding Assessed Tax, Percentage Components of net postretirement medical expense Schedule of Net Benefit Costs [Table Text Block] Accumulated Other Comprehensive Loss Comprehensive Income (Loss) Note [Text Block] Other Liabilities Disclosure [Abstract] Summary of Other Long-Term Liabilities Schedule of Other Assets and Other Liabilities [Table Text Block] Organization, Consolidation and Presentation of Financial Statements [Abstract] Accounting Estimates Use of Estimates, Policy [Policy Text Block] Recently Adopted Accounting Standards and Recent Accounting Pronouncements Not Yet Adopted New Accounting Pronouncements, Policy [Policy Text Block] Accumulated Other Comprehensive Income (Loss) [Table] Accumulated Other Comprehensive Income (Loss) [Table] Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Post-retirement plans Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member] Derivatives designated as cash flow hedges Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] Totals AOCI Attributable to Parent [Member] Accumulated Other Comprehensive Income (Loss) [Line Items] Accumulated Other Comprehensive Income (Loss) [Line Items] AOCI Attributable to Parent, Net of Tax [Roll Forward] AOCI Attributable to Parent, Net of Tax [Roll Forward] Beginning of period Stockholders' Equity Attributable to Parent Other comprehensive income (loss) before reclassifications OCI, before Reclassifications, Net of Tax, Attributable to Parent Amounts reclassified from accumulated other comprehensive loss Reclassification from AOCI, Current Period, Net of Tax, Attributable to Parent Total other comprehensive income (loss), net of tax Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent End of period Other comprehensive income (loss) before reclassifications, tax Other Comprehensive Income (Loss), Tax, Portion Attributable to Parent Fair Value Disclosures [Abstract] Schedule of Recurring Fair Value Measurements Fair Value Measurements, Recurring and Nonrecurring [Table Text Block] Income Tax Disclosure [Abstract] Income Taxes Income Tax Disclosure [Text Block] Deferred rent Deferred Rent Credit, Noncurrent Postretirement benefit obligations Liability, Pension and Other Postretirement and Postemployment Benefits, Noncurrent Other Other Liabilities and Deferred Revenue, Noncurrent Total other long-term liabilities Other Liabilities, Noncurrent Long-term disability obligation Postemployment Benefits Liability, Noncurrent Contingent consideration, liability Business Combination, Contingent Consideration, Liability, Noncurrent Schedule of Business Acquisitions, by Acquisition [Table] Schedule of Business Acquisitions, by Acquisition [Table] Business Acquisition [Axis] Business Acquisition [Axis] Business Acquisition, Acquiree [Domain] Business Acquisition, Acquiree [Domain] Aquilent eGov Holdings, Inc. (d/b/a Aquilent) [Member] eGov Holdings, Inc. (d/b/a Aquilent) Business Acquisition [Line Items] Business Acquisition [Line Items] Acquisition-related contingent consideration Business Combination, Contingent Consideration, Liability Schedule of Disaggregation of Revenue Disaggregation of Revenue [Table Text Block] Summary of Contract Balances Contract with Customer, Asset and Liability [Table Text Block] Schedule of Stock by Class [Table] Schedule of Stock by Class [Table] Class of Stock [Line Items] Class of Stock [Line Items] Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Beginning balance (shares) Shares, Outstanding Issuance of common stock (shares) Stock Issued During Period, Shares, New Issues Stock options exercised (shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period Ending balance (shares) Treasury stock, beginning balance (shares) Treasury Stock, Shares Repurchase of common stock (in shares) Treasury Stock, Shares, Acquired Treasury stock, ending balance (shares) Repurchase of common stock, value, cost method Treasury Stock, Value, Acquired, Cost Method Number of reportable segments Number of Operating Segments Number of employees Entity Number of Employees Schedule of accumulated other comprehensive loss Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] Reclassification out of accumulated other comprehensive loss to net income Reclassification out of Accumulated Other Comprehensive Income [Table Text Block] Employee Benefit Plans Pension and Other Postretirement Benefits Disclosure [Text Block] Payables and Accruals [Abstract] Accounts Payable and Other Accrued Expenses Accounts Payable and Accrued Liabilities Disclosure [Text Block] Stock-Based Compensation Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Schedule of Debt Schedule of Debt [Table Text Block] Schedule of Interest Expense Interest Income and Interest Expense Disclosure [Table Text Block] Fair Value Measurements Fair Value Disclosures [Text Block] 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 and Entity Information [Abstract] Entity Registrant Name Entity Registrant Name Entity Central Index Key Entity Central Index Key Document Type Document Type Document Period End Date Document Period End Date Amendment Flag Amendment Flag Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Current Fiscal Year End Date Current Fiscal Year End Date Entity Filer Category Entity Filer Category Entity Small Business Entity Small Business Entity Emerging Growth Company Entity Emerging Growth Company Entity Listings [Table] Entity Listings [Table] Non-voting common stock, Class B Common Class B [Member] Restricted common stock, Class C Common Class C [Member] Special voting common stock, Class E Common Class E [Member] Classification of common stock that has different rights than Common Class A, B or C shares, representing the voting rights that accompany options that were issued in exchange for old stock rights that existed prior to the merger with The Carlyle Group. Entity Listings [Line Items] Entity Listings [Line Items] Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Reclassification out of Accumulated Other Comprehensive Income [Table] Reclassification out of Accumulated Other Comprehensive Income [Table] Reclassification out of Accumulated Other Comprehensive Income [Axis] Reclassification out of Accumulated Other Comprehensive Income [Axis] Reclassification out of Accumulated Other Comprehensive Income [Domain] Reclassification out of Accumulated Other Comprehensive Income [Domain] Reclassification out of Accumulated Other Comprehensive Income Reclassification out of Accumulated Other Comprehensive Income [Member] Post-retirement Plans Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent [Member] Reclassification out of Accumulated Other Comprehensive Income [Line Items] Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] Income before income taxes Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest Tax benefit Income Tax Expense (Benefit) Net of tax Net Income (Loss) Attributable to Parent Statement of Financial Position [Abstract] Common stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Common stock, shares authorized Common Stock, Shares Authorized Common stock, shares issued Common Stock, Shares, Issued Common stock, shares outstanding Common Stock, Shares, Outstanding Treasury stock, shares Revenue, amount of remaining performance obligation Revenue, Remaining Performance Obligation, Amount Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [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 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 Remaining performance obligation, percentage Revenue, Remaining Performance Obligation, Percentage Contract with customer, liability, revenue recognized Contract with Customer, Liability, Revenue Recognized Statement of Cash Flows [Abstract] Cash flows from operating activities Net Cash Provided by (Used in) Operating Activities [Abstract] Net income 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] Depreciation and amortization Depreciation, Depletion and Amortization Stock-based compensation expense Share-based Compensation Excess tax benefits from stock-based compensation Excess Tax Benefit from Share-based Compensation, Operating Activities Amortization of debt issuance costs and loss on extinguishment Amortization Of Financing Costs And Discounts and Gain/Loss on Extinguishment of Debt Amortization Of Financing Costs And Discounts and Loss on Extinguishment of Debt Losses on dispositions Gain (Loss) on Disposition of Assets Changes in assets and liabilities: Increase (Decrease) in Operating Capital [Abstract] Accounts receivable Increase (Decrease) in Accounts Receivable Prepaid expenses and other current assets Increase (Decrease) in Prepaid Expense and Other Assets Other long-term assets Increase (Decrease) in Other Noncurrent Assets Accrued compensation and benefits Increase (Decrease) in Employee Related Liabilities Accounts payable and other accrued expenses Increase (Decrease) in Accounts Payable and Accrued Liabilities Accrued interest Increase (Decrease) in Interest Payable, Net Other current liabilities Increase (Decrease) in Other Operating Liabilities Other long-term liabilities Increase (Decrease) in Other Noncurrent Liabilities Net cash provided by operating activities Net Cash Provided by (Used in) Operating Activities Cash flows from investing activities Net Cash Provided by (Used in) Investing Activities [Abstract] Purchases of property, equipment, and software Payments to Acquire Property, Plant, and Equipment Payments for business acquisitions, net of cash acquired Payments to Acquire Businesses, Net of Cash Acquired Net cash used in investing activities Net Cash Provided by (Used in) Investing Activities Cash flows from financing activities Net Cash Provided by (Used in) Financing Activities [Abstract] Proceeds from issuance of common stock Proceeds from Issuance of Common Stock Stock option exercises Proceeds from Stock Options Exercised Repurchases of common stock Payments for Repurchase of Common Stock Cash dividends paid Dividend equivalents paid to option holders Payments of Capital Distribution Repayment of debt Repayments of Debt Proceeds from debt issuance Proceeds from Issuance of Long-term Debt Payment on contingent liabilities from acquisition Payment for Contingent Consideration Liability, Financing Activities Net cash used in financing activities Net Cash Provided by (Used in) Financing Activities Net increase in cash and cash equivalents Cash and Cash Equivalents, Period Increase (Decrease) Cash and cash equivalents––beginning of period Cash and Cash Equivalents, at Carrying Value Cash and cash equivalents––end of period Supplemental disclosures of cash flow information Supplemental Cash Flow Information [Abstract] Cash paid during the period for: Cash Payments Abstract Cash paid during the period for: Interest Interest Paid, Excluding Capitalized Interest, Operating Activities Income taxes Income Taxes Paid, Net Supplemental disclosures of non-cash investing and financing activities Noncash Investing and Financing Items [Abstract] Noncash financing activities Noncash Financing Activities Noncash Financing Activities Litigation Case [Axis] Litigation Case [Axis] Litigation Case [Domain] Litigation Case [Domain] 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] Former stockholder litigation Former Stockholder Litigation [Member] Former Stockholder Litigation [Member] Litigation Court [Axis] Litigation Court [Axis] Litigation Court [Axis] Litigation Court Type [Domain] Litigation Court Type [Domain] Litigation Court Type [Domain] United States District Court for Southern District of New York United States District Court for Southern District of New York [Member] United States District Court for Southern District of New York [Member] Loss contingencies, number of plaintiffs Loss Contingency, Number of Plaintiffs Loss contingencies, new claims filed, number Loss Contingency, New Claims Filed, Number Loss contingencies, claims amended, number Loss Contingency, Claims Amended, Number Loss Contingency, Claims Amended, Number Loss contingencies, claims dismissed, number Loss Contingency, Claims Settled and Dismissed, Number Loss contingency, claims amended, number of claims consolidated Loss Contingency, Claims Amended, Number Of Claims Consolidated Loss Contingency, Claims Amended, Number Of Claims Consolidated Loss contingencies, claims settled, number Loss Contingency, Claims Settled, Number Loss contingencies, pending claims, number Loss Contingency, Pending Claims, Number Vendor payables Accounts Payable, Trade, Current Accrued expenses Accrued Liabilities, Current Total accounts payable and other accrued expenses Accounts Payable and Accrued Liabilities, Current Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Unrecognized compensation cost related to unvested stock-based compensation agreements Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized Unrecognized compensation cost, amortization period Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition Derivative Instruments and Hedging Activities Disclosure [Abstract] Derivatives Derivative Instruments and Hedging Activities Disclosure [Text Block] Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] ASSETS Assets [Abstract] Current assets: Assets, Current [Abstract] Cash and cash equivalents Accounts receivable, net of allowance Prepaid expenses and other current assets Prepaid Expense and Other Assets, Current Total current assets Assets, Current Property and equipment, net of accumulated depreciation Property, Plant and Equipment, Net Intangible assets, net of accumulated amortization Intangible Assets, Net (Excluding Goodwill) Goodwill Goodwill Other long-term assets Other Assets, Noncurrent Total assets Assets LIABILITIES AND STOCKHOLDERS’ EQUITY Liabilities and Equity [Abstract] Current liabilities: Liabilities, Current [Abstract] Current portion of long-term debt Accounts payable and other accrued expenses Accrued compensation and benefits Other current liabilities Other Liabilities, Current Total current liabilities Liabilities, Current Other long-term liabilities Total liabilities Liabilities Commitments and contingencies (Note 18) Commitments and Contingencies Stockholders’ equity: Stockholders' Equity Attributable to Parent [Abstract] Common stock, Class A — $0.01 par value — authorized, 600,000,000 shares; issued, 159,124,212 shares at September 30, 2018 and 158,028,673 shares at March 31, 2018; outstanding, 142,550,779 shares at September 30, 2018 and 143,446,539 shares at March 31, 2018 Common Stock, Value, Issued Treasury stock, at cost — 16,573,433 shares at September 30, 2018 and 14,582,134 shares at March 31, 2018 Treasury Stock, Value Additional paid-in capital Additional Paid in Capital, Common Stock Retained earnings Retained Earnings (Accumulated Deficit) Accumulated other comprehensive loss Accumulated Other Comprehensive Income (Loss), Net of Tax Total stockholders’ equity Total liabilities and stockholders’ equity Liabilities and Equity Earnings Per Share Earnings Per Share [Text Block] Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value Measurements, Recurring and Nonrecurring [Table] Liability Class [Axis] Liability Class [Axis] Fair Value by Liability Class [Domain] Fair Value by Liability Class [Domain] Other noncurrent liabilities Other Noncurrent Liabilities [Member] Measurement Frequency [Axis] Measurement Frequency [Axis] Fair Value, Measurement Frequency [Domain] Fair Value, Measurement Frequency [Domain] Fair Value, Measurements, Recurring Fair Value, Measurements, Recurring [Member] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Fair Value, Measurements, Fair Value Hierarchy [Domain] Fair Value Hierarchy and NAV [Domain] Level 1 Fair Value, Inputs, Level 1 [Member] Level 2 Fair Value, Inputs, Level 2 [Member] Level 3 Fair Value, Inputs, Level 3 [Member] 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] Assets, Fair Value Disclosure [Abstract] Assets, Fair Value Disclosure [Abstract] Current derivative instruments Derivative Asset, Current Long term derivative instruments Derivative Asset, Noncurrent Long term deferred compensation costs Total Assets Other Assets, Fair Value Disclosure Liabilities, Fair Value Disclosure [Abstract] Liabilities, Fair Value Disclosure [Abstract] Long term deferred compensation costs Total Liabilities Financial Liabilities Fair Value Disclosure Other Long-Term Liabilities Other Liabilities Disclosure [Text Block] Summary of Stock-Based Compensation Expense Recognized in the Condensed Consolidated Statements of Operations Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table Text Block] Schedule of Unrecognized Compensation Cost Schedule of Unrecognized Compensation Cost, Nonvested Awards [Table Text Block] Summary of Grants of Restricted Stock Units and Restricted Stock Awards Schedule of Share-based Compensation, Restricted Stock and Restricted Stock Units Activity [Table Text Block] Debt Debt Disclosure [Text Block] Operating Loss Carryforwards [Table] Operating Loss Carryforwards [Table] Subsequent Event Type [Axis] Subsequent Event Type [Axis] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Subsequent Event Subsequent Event [Member] Adjustments for Change in Accounting Principle [Axis] Adjustments for Change in Accounting Principle [Axis] Adjustments for Change in Accounting Principle [Domain] Adjustments for Change in Accounting Principle [Domain] Revenue Recognition For Income Tax Purposes, Unbilled Receivables Revenue Recognition For Income Tax Purposes, Unbilled Receivables [Member] Revenue Recognition For Income Tax Purposes, Unbilled Receivables [Member] Scenario [Axis] Scenario [Axis] Scenario, Unspecified [Domain] Scenario, Unspecified [Domain] Scenario, Forecast Scenario, Forecast [Member] Tax Period [Axis] Tax Period [Axis] Tax Period [Domain] Tax Period [Domain] Tax Years 2013-2015 Tax Years 2013-2015 [Member] Tax Years 2013-2015 [Member] Tax Years 2016-2018 Tax Years 2016-2018 [Member] Tax Years 2016-2018 [Member] Operating Loss Carryforwards [Line Items] Operating Loss Carryforwards [Line Items] Tax Act, measurement period adjustment to executive compensation Tax Cuts and Jobs Act of 2017, Incomplete Accounting, Measurement Period Adjustment, Executive Compensation Tax Cuts and Jobs Act of 2017, Incomplete Accounting, Measurement Period Adjustment, Executive Compensation Tax Act, measurement period adjustment to income tax expense Tax Cuts and Jobs Act of 2017, Incomplete Accounting, Adjustment To Income Tax Expense (Benefit) Tax Cuts and Jobs Act of 2017, Incomplete Accounting, Adjustment To Income Tax Expense (Benefit) Tax Act, effective tax rate, percent Effective Income Tax Rate Reconciliation, Tax Cuts and Jobs Act of 2017, Percent Effective Income Tax Rate Reconciliation, Tax Cuts and Jobs Act of 2017, Percent Income tax benefit Effective income tax rate Effective Income Tax Rate Reconciliation, Percent Income tax assessments Income Tax Examination, Estimate of Possible Loss Income tax uncertainty Liability for Uncertainty in Income Taxes, Noncurrent Schedule of Accounts Receivable, Net of Allowance Schedule of Accounts, Notes, Loans and Financing Receivable [Table Text Block] Revenue, Initial Application Period Cumulative Effect Transition [Table] Revenue, Initial Application Period Cumulative Effect Transition [Table] Restatement [Axis] Restatement [Axis] Restatement [Domain] Restatement [Domain] Restatement Adjustment Restatement Adjustment [Member] Adjustments for New Accounting Pronouncements [Axis] Adjustments for New Accounting Pronouncements [Axis] Type of Adoption [Domain] Type of Adoption [Domain] Accounting Standards Update 2014-09 Accounting Standards Update 2014-09 [Member] Accounting Standards Update 2017-07 Accounting Standards Update 2017-07 [Member] Revenue, Initial Application Period Cumulative Effect Transition [Line Items] Revenue, Initial Application Period Cumulative Effect Transition [Line Items] Increase (decrease) in retained earnings Cumulative effect on retained earnings Cumulative Effect on Retained Earnings, Net of Tax Reclassification of net periodic benefit cost Net Periodic Defined Benefits Expense (Reversal of Expense), Excluding Service Cost Component Income Statement [Abstract] Operating costs and expenses: Costs and Expenses [Abstract] Cost of revenue Cost of Goods and Services Sold Billable expenses Billable Expenses Billable expenses include direct subcontractor expenses, travel expenses, and other expenses incurred to perform on contracts. General and administrative expenses General and Administrative Expense Depreciation and amortization Depreciation, Depletion and Amortization, Nonproduction Total operating costs and expenses Costs and Expenses Operating income Operating Income (Loss) Interest expense Other income (expense), net Other Nonoperating Income (Expense) Income before income taxes Income tax expense Net income Earnings per common share (Note 3): Dividends declared per share (in dollars per share) Common Stock, Dividends, Per Share, Declared Stockholders' Equity Stockholders' Equity Note Disclosure [Text Block] Reconciliation of the income used to compute basic and diluted EPS Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Common stock purchased by employees (in shares) Stock Issued During Period, Shares, Employee Stock Purchase Plans Business Overview Nature of Operations [Text Block] Letter of Credit Letter of Credit [Member] Delayed Draw Facility Delayed Draw Facility [Member] Delayed Draw Facility [Member] Senior Notes due 2025 Variable Rate [Axis] Variable Rate [Axis] Variable Rate [Domain] Variable Rate [Domain] London Interbank Offered Rate (LIBOR) London Interbank Offered Rate (LIBOR) [Member] Overnight Federal Funds Rate Overnight Federal Funds Rate [Member] Overnight Federal Funds Rate Base Rate Base Rate [Member] Range [Axis] Range [Axis] Range [Domain] Range [Domain] Minimum Minimum [Member] Maximum Maximum [Member] Revolving credit facility, maximum borrowing capacity Line of Credit Facility, Maximum Borrowing Capacity Long-term debt, basis spread on variable rate Debt Instrument, Basis Spread on Variable Rate Number of draws allowed on facility Line Of Credit Facility, Number Of Draws Allowed On Facility Line Of Credit Facility, Number Of Draws Allowed On Facility Minimum amount per draw on facility Line Of Credit Facility, Minimum Amount Per Draw On Facility Line Of Credit Facility, Minimum Amount Per Draw On Facility Long-term debt, maximum expanded loan facility Long-term Debt, Maximum Expanded Loan Facility Long-Term Debt, Maximum Expanded Loan Facility 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 Net secured leverage ratio Debt Instrument, Net Secured Leverage Ratio, Maximum Debt Instrument, Net Secured Leverage Ratio, Maximum Commitment fee percentage Line of Credit Facility, Commitment Fee Percentage Quarterly periodic payment percentage, principal Debt Instrument, Quarterly Periodic Payment Percentage, Principal Debt Instrument, Quarterly Periodic Payment Percentage, Principal Proceeds from lines of credit Proceeds from Lines of Credit Revolving credit facility, amount outstanding Long-term Line of Credit Term loan, face amount Debt Instrument, Face Amount Debt instrument, stated percentage Debt Instrument, Interest Rate, Stated Percentage Debt issuance costs Debt Issuance Costs, Gross Interest Interest Paid, Including Capitalized Interest, Operating and Investing Activities Notional amount of interest rate swaps Derivative, Notional Amount Accrued Compensation and Benefits Compensation Related Costs, General [Text Block] Related-Party Transactions Related Party Transactions Disclosure [Text Block] Restricted stock units (RSUs) Restricted Stock Units (RSUs) [Member] Stock options outstanding (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number Stock options outstanding, unvested (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares Restricted stock granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Stock price on grant date (in dollars per share) Share Price 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 Statement of Comprehensive Income [Abstract] Other Comprehensive Income (Loss), Net of Tax [Abstract] Other Comprehensive Income (Loss), Net of Tax [Abstract] Change in unrealized gain (loss) on derivatives designated as cash flow hedges Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax Change in postretirement plan costs Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, after Tax Comprehensive income Comprehensive Income (Loss), Net of Tax, Attributable to Parent Derivative [Table] Derivative [Table] Hedging Designation [Axis] Hedging Designation [Axis] Hedging Designation [Domain] Hedging Designation [Domain] Designated as Hedging Instrument Designated as Hedging Instrument [Member] Hedging Relationship [Axis] Hedging Relationship [Axis] Hedging Relationship [Domain] Hedging Relationship [Domain] Cash Flow Hedging Cash Flow Hedging [Member] Balance Sheet Location [Axis] Balance Sheet Location [Axis] Balance Sheet Location [Domain] Balance Sheet Location [Domain] Other Current Assets Other Current Assets [Member] Long-term assets Other Noncurrent Assets [Member] Derivative Instrument [Axis] Derivative Instrument [Axis] Derivative Contract [Domain] Derivative Contract [Domain] Interest Rate Swap Interest Rate Swap [Member] Derivative [Line Items] Derivative [Line Items] Notional amount Fair value of derivative assets Derivative Instruments in Hedges, Assets, at Fair Value Gain (loss) recognized in AOCI Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax Amounts reclassified into earnings Interest Rate Cash Flow Hedge Gain (Loss) Reclassified to Earnings, Net Ineffectiveness recognized in earnings Gain (Loss) on Cash Flow Hedge Ineffectiveness, Net 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 Schedule of Accounts Payable and Accrued Liabilities Schedule of Accounts Payable and Accrued Liabilities [Table Text Block] Contract assets: Contract with Customer, Asset, Net [Abstract] Current Long-term Total Contract with Customer, Asset, Net Contract liabilities: Contract with Customer, Liability [Abstract] Advance payments, billings in excess of costs incurred and deferred revenue Contract with Customer, Liability Previously Reported Previously Reported [Member] Topic 606 ASU 2017-07 Operating income Earnings per common share, basic (in dollars per share) Earnings per common share, diluted (in dollars per shares) Schedule of New Accounting Pronouncements and Changes in Accounting Principles Schedule of New Accounting Pronouncements and Changes in Accounting Principles [Table Text Block] Revenue Revenue from Contract with Customer [Text Block] Basis of Presentation Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block]