Mantech International (MANT) 10-K 19 Feb 21 2020 FY Annual report Financial data

Cover Page

Cover Page - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Feb. 17, 2021	Jun. 30, 2020
Entity Information [Line Items]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2020
Document Transition Report	false
Entity File Number	000-49604
Entity Registrant Name	ManTech International Corporation
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	22-1852179
Entity Address, Address Line One	2251 Corporate Park Drive
Entity Address, City or Town	Herndon
Entity Address, State or Province	VA
Entity Address, Postal Zip Code	20171
City Area Code	(703)
Local Phone Number	218-6000
Title of 12(b) Security	Class A Common Stock
Trading Symbol	MANT
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float			$ 1,850
Documents Incorporated by Reference	Certain portions of the definitive Proxy Statement to be filed with the Securities Exchange Commission pursuant to Regulation 14A in connection with the registrant's 2021 Annual Meeting of Stockholders, to be filed subsequent to the date hereof, are incorporated by reference into Part III (Items 10, 11, 12, 13 and 14) of this Annual Report on Form 10-K. Such definitive Proxy Statement will be filed with the Commission not later than 120 days after the end of the fiscal year covered by this Annual Report on Form 10-K.
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Current Fiscal Year End Date	--12-31
Entity Central Index Key	0000892537
Common Stock, Class A
Entity Information [Line Items]
Common Stock, Shares Outstanding		27,325,395
Common Stock, Class B
Entity Information [Line Items]
Common Stock, Shares Outstanding		13,176,695

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
ASSETS
Cash and cash equivalents	$ 41,193	$ 8,854
Receivables—net	400,621	398,976
Prepaid expenses	26,243	20,030
Taxes receivable—current	21,968	21,996
Other current assets	6,354	4,878
Total Current Assets	496,379	454,734
Goodwill	1,237,894	1,191,259
Other intangible assets—net	202,231	196,778
Property and equipment—net	121,296	85,631
Operating lease right of use assets	94,825	117,728
Employee supplemental savings plan assets	37,848	36,777
Investments	11,549	11,550
Other assets	11,642	13,457
TOTAL ASSETS	2,213,664	2,107,914
LIABILITIES
Accounts payable	142,360	138,029
Accrued salaries and related expenses	123,953	97,298
Contract liabilities	37,218	27,620
Operating lease obligations—current	30,105	29,047
Accrued expenses and other current liabilities	15,177	7,987
Total Current Liabilities	348,813	299,981
Deferred income taxes	141,638	131,782
Operating lease obligations—long term	80,242	103,148
Accrued retirement	36,310	35,552
Long term debt	15,000	36,500
Other long-term liabilities	12,249	10,309
TOTAL LIABILITIES	634,252	617,272
COMMITMENTS AND CONTINGENCIES
STOCKHOLDERS' EQUITY
Additional paid-in capital	545,717	525,851
Treasury stock	(9,158)	(9,158)
Retained earnings	1,042,676	973,767
Accumulated other comprehensive loss	(230)	(222)
TOTAL STOCKHOLDERS' EQUITY	1,579,412	1,490,642
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	2,213,664	2,107,914
Common Stock, Class A
STOCKHOLDERS' EQUITY
Common stock	275	272
TOTAL STOCKHOLDERS' EQUITY	275	272
Common Stock, Class B
STOCKHOLDERS' EQUITY
Common stock	132	132
TOTAL STOCKHOLDERS' EQUITY	$ 132	$ 132

Consolidated Balance Sheets Par

Consolidated Balance Sheets Parenthetical - $ / shares	Dec. 31, 2020	Dec. 31, 2019
Treasury Stock, Shares	244,113	244,113
Common Stock, Class A
Common Stock, Par Value Per Share	$ 0.01	$ 0.01
Common Stock, Shares Authorized	150,000,000	150,000,000
Common Stock, Shares Issued	27,538,474	27,235,860
Common Stock, Shares Outstanding	27,294,361	26,991,747
Common Stock, Class B
Common Stock, Par Value Per Share	$ 0.01	$ 0.01
Common Stock, Shares Authorized	50,000,000	50,000,000
Common Stock, Shares Issued	13,176,695	13,187,195
Common Stock, Shares Outstanding	13,176,695	13,187,195

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
REVENUES	$ 2,518,384	$ 2,222,559	$ 1,958,557
Cost of services	2,138,791	1,893,461	1,678,100
General and administrative expenses	221,544	190,773	167,715
OPERATING INCOME	158,049	138,325	112,742
Interest expense	(1,900)	(2,594)	(2,378)
Interest income	247	450	161
Other income (expense), net	1	(83)	80
INCOME FROM OPERATIONS BEFORE INCOME TAXES AND EQUITY METHOD INVESTMENTS	156,397	136,098	110,605
Provision for income taxes	(35,865)	(22,212)	(28,530)
Equity in earnings (losses) of unconsolidated subsidiaries	(2)	4	22
NET INCOME	$ 120,530	$ 113,890	$ 82,097
Common Stock, Class A
BASIC EARNINGS PER SHARE:
Basic earnings per share	$ 2.99	$ 2.85	$ 2.08
DILUTED EARNINGS PER SHARE:
Diluted earnings per share	2.97	2.83	2.06
Common Stock, Class B
BASIC EARNINGS PER SHARE:
Basic earnings per share	2.99	2.85	2.08
DILUTED EARNINGS PER SHARE:
Diluted earnings per share	$ 2.97	$ 2.83	$ 2.06

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Net income	$ 120,530,000	$ 113,890,000	$ 82,097,000
OTHER COMPREHENSIVE INCOME (LOSS):
Translation adjustments, net of tax	(41,000)	(77,000)	(27,000)
Actuarial gain (loss) on defined benefit pension plans, net of tax	33,000	(19,000)	245,000
Cumulative-effect adjustment for adoption of Accounting Standard Update 2018-02	0	(24,000)	0
Total other comprehensive income (loss)	(8,000)	(120,000)	218,000
COMPREHENSIVE INCOME	$ 120,522,000	$ 113,770,000	$ 82,315,000

Consolidated Statement of Chang

Consolidated Statement of Changes in Stockholders' Equity Statement - USD ($)	Total	Common Stock, Class A	Common Stock, Class B	Additional Paid-In Capital	Treasury Stock, at cost	Retained Earnings	Accumulated Other Comprehensive Loss
Stockholders' Equity		$ 263,000	$ 132,000	$ 492,030,000	$ (9,158,000)	$ 860,027,000	$ (320,000)
Stock option exercises		4,000		12,591,000
Stock-based compensation expense		1,000		5,072,000
Payment consideration to tax authority on employees' behalf				(2,723,000)
Net income	$ 82,097,000					82,097,000
Dividends						(39,627,000)
Cumulative-effect adjustment for adoption of Accounting Standards Update 2014-09						587,000
Translation adjustments, net of tax	(27,000)						(27,000)
Actuarial gain (loss) on defined benefit pension plans, net of tax	245,000						245,000
Cumulative-effect adjustment for adoption of Accounting Standard Update 2018-02	0						0
Stockholders' Equity	1,401,194,000	268,000	132,000	506,970,000	(9,158,000)	903,084,000	(102,000)
Stock option exercises		3,000		12,892,000
Stock-based compensation expense		1,000		7,492,000
Payment consideration to tax authority on employees' behalf				(1,503,000)
Net income	113,890,000					113,890,000
Dividends						(43,207,000)
Cumulative-effect adjustment for adoption of Accounting Standards Update 2014-09						0
Translation adjustments, net of tax	(77,000)						(77,000)
Actuarial gain (loss) on defined benefit pension plans, net of tax	(19,000)						(19,000)
Cumulative-effect adjustment for adoption of Accounting Standard Update 2018-02	(24,000)						(24,000)
Stockholders' Equity	1,490,642,000	272,000	132,000	525,851,000	(9,158,000)	973,767,000	(222,000)
Stock option exercises		2,000		10,247,000
Stock-based compensation expense		1,000		11,365,000
Payment consideration to tax authority on employees' behalf				(1,746,000)
Net income	120,530,000					120,530,000
Dividends						(51,621,000)
Cumulative-effect adjustment for adoption of Accounting Standards Update 2014-09						0
Translation adjustments, net of tax	(41,000)						(41,000)
Actuarial gain (loss) on defined benefit pension plans, net of tax	33,000						33,000
Cumulative-effect adjustment for adoption of Accounting Standard Update 2018-02	0						0
Stockholders' Equity	$ 1,579,412,000	$ 275,000	$ 132,000	$ 545,717,000	$ (9,158,000)	$ 1,042,676,000	$ (230,000)

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
CASH FLOWS FROM (USED IN) OPERATING ACTIVITIES:
Net income	$ 120,530,000	$ 113,890,000	$ 82,097,000
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	70,300,000	55,879,000	52,569,000
Noncash lease expense	28,169,000	27,619,000	0
Deferred income taxes	9,856,000	15,739,000	11,762,000
Stock-based compensation expense	11,366,000	7,493,000	5,073,000
Bad debt expense	5,244,000	3,000,000	0
Contract loss reserve	(372,000)	(1,481,000)	0
(Gain) loss on sale and retirement of property and equipment	(172,000)	171,000	75,000
Equity in (earnings) losses of unconsolidated subsidiaries	2,000	(4,000)	(22,000)
Change in assets and liabilities—net of effects from acquired businesses:
Receivables-net	1,298,000	24,660,000	(87,098,000)
Prepaid expenses	(5,963,000)	419,000	(613,000)
Taxes receivable—current	28,000	(21,996,000)	18,732,000
Other current assets	(987,000)	4,060,000	(1,321,000)
Employee supplemental savings plan asset	(5,208,000)	(6,297,000)	1,754,000
Other long-term assets	(1,827,000)	97,000	(953,000)
Accounts payable	(303,000)	14,707,000	3,904,000
Accrued salaries and related expenses	24,666,000	2,796,000	2,095,000
Contract liabilities	9,149,000	(589,000)	6,110,000
Accrued expenses and other current liabilities	9,248,000	(3,857,000)	1,423,000
Operating lease obligations	(31,055,000)	(28,520,000)	0
Accrued retirement	758,000	4,553,000	(3,518,000)
Other long-term liabilities	2,010,000	9,380,000	1,384,000
Other	507,000	(313,000)	(14,000)
Net cash flow from operating activities	247,244,000	221,406,000	93,439,000
CASH FLOWS FROM (USED IN) INVESTING ACTIVITIES:
Acquisition of businesses-net of cash acquired	(78,815,000)	(152,851,000)	(5,279,000)
Purchases of property and equipment	(71,129,000)	(54,795,000)	(30,114,000)
Investment in capitalized software for internal use	(5,193,000)	(3,677,000)	(5,018,000)
Proceeds from corporate owned life insurance	4,137,000	21,000	1,300,000
Proceeds from sale of property and equipment	869,000	0	0
Deferred contract costs	0	(3,878,000)	(5,233,000)
Proceeds from equity method investment	0	283,000	0
Net cash used in investing activities	(150,131,000)	(214,897,000)	(44,344,000)
CASH FLOWS FROM (USED IN) FINANCING ACTIVITIES:
Borrowings under revolving credit facility	302,500,000	624,000,000	575,500,000
Repayments under revolving credit facility	(324,000,000)	(595,000,000)	(599,000,000)
Dividends paid	(51,618,000)	(43,205,000)	(39,624,000)
Proceeds from exercise of stock options	10,249,000	12,895,000	12,595,000
Payment consideration to tax authority on employee's behalf	(1,746,000)	(1,503,000)	(2,723,000)
Principal paid on financing leases	(159,000)	(136,000)	0
Net cash used in financing activities	(64,774,000)	(2,949,000)	(53,252,000)
NET CHANGE IN CASH AND CASH EQUIVALENTS	32,339,000	3,560,000	(4,157,000)
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD	8,854,000	5,294,000	9,451,000
CASH AND CASH EQUIVALENTS, END OF PERIOD	41,193,000	8,854,000	5,294,000
SUPPLEMENTAL CASH FLOW INFORMATION
Cash paid for interest	1,819,000	2,436,000	2,315,000
Noncash investing and financing activities:
Noncash investing activities	5,480,000	5,981,000	340,000
Operating lease obligations arising from obtaining right of use assets	6,459,000	31,010,000	0
Finance lease obligations arising from obtaining right of use assets	$ 107,000	$ 368,000	$ 0

Description of the Business (No

Description of the Business (Notes)	12 Months Ended
	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of the Business [Text Block]	Description of the Business ManTech International Corporation (depending on the circumstances, “ManTech” “Company” “we” “our” “ours” or “us”) provides mission-focused technology solutions and services for U.S. defense, intelligence community and federal civilian agencies. We excel in full-spectrum cyber, secure mission & enterprise IT, advanced data analytics, software and systems development, intelligent systems engineering, intelligence mission support and mission operations.

Summary of Significant Accounti

Summary of Significant Accounting Policies (Notes)	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Significant Accounting Policies [Text Block]	Summary of Significant Accounting Policies Principles of Consolidation - Our consolidated financial statements include the accounts of ManTech International Corporation, subsidiaries we control and variable interest entities that are required to be consolidated. All intercompany accounts and transactions have been eliminated. Use of Accounting Estimates - We prepare our consolidated financial statements in conformity with U.S. GAAP, which requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. These estimates involve judgments with respect to, among other things, various future economic factors that are difficult to predict and are beyond our control. Therefore, actual amounts could differ from these estimates. Business Combinations - The accounting for our business combinations consists of allocating the purchase price to tangible and intangible assets acquired and liabilities assumed based on their estimated fair values, with the excess recorded as goodwill. We have up to one year from the acquisition date to use information as of each acquisition date to adjust the fair value of the acquired assets and liabilities, which may result in material changes to their recorded values with an offsetting adjustment to goodwill. Determining the fair value of assets acquired and liabilities assumed requires significant judgment, which includes, among other factors, analysis of historical performance and estimates of future performance. In some cases, we have used discounted cash flow analyses, which were based on our best estimate of future revenue, earnings and cash flows as well as our discount rate, adjusted for risk, and estimated attrition rates. Fair Value of Financial Instruments - The carrying value of our cash and cash equivalents, accounts receivable, accounts payable and accrued expenses approximate their fair value because of the short-term nature of these amounts. Cash and Cash Equivalents - For the purpose of reporting cash flows, cash and cash equivalents include cash on hand, amounts due from banks and short-term investments with maturity dates of three months or less at the date of purchase. Contract Assets - Amounts are invoiced as work progresses in accordance with agreed-upon contractual terms, either at periodic intervals or upon achievement of contractual milestones. Generally, revenue recognition occurs before billing, resulting in contract assets. These contract assets are referred to as unbilled receivables and are reported within receivables, net on our consolidated balance sheet. Billed Receivables - Amounts billed and due from our customers are classified as billed receivables and are reported within receivables, net on the consolidated balance sheet. The portion of the payments retained by the customer until final contract settlement is not considered a significant financing component because the intent is to protect the customer. Goodwill - The purchase price of an acquired business is allocated to the tangible assets, financial assets and separately recognized intangible assets acquired less liabilities assumed based upon their respective fair values, with the excess recorded as goodwill. We review goodwill at least annually for impairment, or whenever events or circumstances indicate that the carrying value of long-lived assets may not be fully recoverable. We have elected to perform this annual review as of October 31 st of each calendar year. In reviewing goodwill for impairment, we have the option to first assess qualitative factors to determine whether the existence of events or circumstances leads to a determination that it is more likely than not that the estimated fair value of a reporting unit is less than its carrying amount. If we elect to perform a qualitative assessment and determine that it is more likely than not that the fair value of the reporting unit is less than its carry amount, then we will perform the quantitative impairment test (described below). We also may bypass the qualitative assessment for any reporting unit in any period and, proceed directly to perform the quantitative impairment test. The quantitative goodwill impairment test, is used to identify both the existence of impairment and the amount of the impairment loss, compares the fair value of a reporting unit with its carrying amount, including goodwill. If the fair value of a reporting unit exceeds its carrying amount, the goodwill of the reporting unit is not impaired. If the carrying amount of a reporting unit exceeds its fair value, an impairment loss will be recognized in the amount equal to that excess, limited to the total amount of goodwill allocated to that reporting unit. The fair values of the reporting units are determined based on a weighting of the income approach, market approach and market transaction approach. The income approach is a valuation technique in which fair value is based from forecasted future cash flow discounted at the appropriate rate of return commensurate with the risk as well as current rates of return for equity and debt capital as of the valuation date. The forecast used in our estimation of fair value was developed by management based on a contract basis, incorporating adjustments to reflect known contract and market considerations (such as reductions and uncertainty in government spending, pricing pressure and opportunities). The discount rate utilizes a risk adjusted weighted average cost of capital. The market approach is a valuation technique in which the fair value is calculated based on market prices realized in an actual arm's length transaction. The technique consists of undertaking a detailed market analysis of publicly traded companies that provides a reasonable basis for comparison to us. Valuation ratios, which relate market prices to selected financial statistics derived from comparable companies, are selected and applied to us after consideration of adjustments for financial position, growth, market, profitability and other factors. The market transaction approach is a valuation technique in which the fair value is calculated based on market prices realized in actual arm's length transactions. The technique consists of undertaking a detailed market analysis of merged and acquired companies that provides a reasonable basis for comparison to us. Valuation ratios, which relate market prices to selected financial statistics derived from comparable companies, are selected and applied to us after consideration of adjustments for financial position, growth, market, profitability and other factors. To assess the reasonableness of the calculated reporting unit fair values, we compare the sum of the reporting units' fair values to our market capitalization (per share stock price times the number of shares outstanding) and calculate an implied control premium (the excess of the sum of the reporting units' fair values over the market capitalization) and then assess the reasonableness of our implied control premium. Other Intangible Assets - Contract rights and other intangible assets are amortized primarily using the pattern of benefits method over periods ranging from 1 year to 25 years. We account for the cost of computer software developed or obtained for internal use in accordance with Accounting Standards Codification (ASC) 350-985, Intangibles - Goodwill and Other - Software . These capitalized software costs are included in other intangible assets, net. We account for software development costs related to software products for sale, lease or otherwise marketed in accordance with ASC 985-20, Software - Costs of Software to Be Sold, Leased, or Marketed . For projects fully funded by us, development costs are capitalized from the point of demonstrated technological feasibility until the point in time that the product is available for general release to customers. Once the product is available for general release, capitalized costs are amortized based on units sold or on a straight-line basis over a period of 5 years or other such shorter period as may be required. Leases - We adopted ASC 842, Leases , on January 1, 2019. We elected to apply the provisions of the standard as of the date of adoption, and, therefore, have not restated prior comparative periods. Upon adoption, we recorded operating lease obligations of $129.6 million and operating lease right of use (ROU) assets of $118.7 million. We elected the practical expedient to recognize the lease payments related to short-term leases as profit or loss on a straight-line basis over the lease term and variable lease payments in the period in which the obligation for those payments are incurred. We also elected the following transition related practical expedients: not to reassess whether expired or existing contracts are or contain leases, not to reassess lease classification as determined under ASC 840 and not to reassess initial direct costs from any existing lease. We elected the practical expedient as an accounting election not to separate nonlease components from lease components on all classes of underlying assets. Our leases include nonlease components such as common area maintenance, utilities and operating expenses. Additionally, we implemented internal controls and key system functionality to enable the preparation of financial information upon adoption. ASC 842 had a material impact on our consolidated balance sheet, but did not have an impact on our consolidated income statement. The most significant impact was the recognition of ROU assets and lease obligations for operating leases, while our accounting for finance leases remained substantially unchanged. We determine whether a contract is or contains a lease at inception. A contract is or contains a lease if the contract conveys the right to control the use of identified property or equipment (an identified asset) for a period of time in exchange for consideration. We have the right to control the use of the identified asset when we have both of the following: the right to obtain substantially all of the economic benefits from use of the identified asset and the right to direct the use of the identified asset. In making this determination, we consider all relevant facts and circumstances. We reassess whether a contract is or contains a lease only if the terms and conditions of the contract are changed. We account for lease components and nonlease components associated with a lease as a single lease component. Operating leases are included in Operating lease right of use assets, Operating lease obligations—current and Operating lease obligations—long term on our consolidated balance sheets. Finance leases are included in Property and equipment—net, Accrued expenses and other current liabilities and Other long-term liabilities on our consolidated balance sheets. Our ROU asset is recognized as the lease obligation, any initial direct costs and any prepaid lease payments, less any lease incentives. Our lease obligations are recognized based on the present value of the future minimum lease payments over the lease term at commencement date. Our lease payments consist of amounts relating to the use of the underlying asset during the lease term, specifically fixed payments, payments to be made in optional periods when we are reasonably certain to exercise an option to extend the lease or not to exercise an option to terminate the lease and the amounts probable of being owed by us under residual guarantees. Our variable lease payments are excluded in measuring ROU assets and lease obligations because they do not depend on an index or a rate or are not in substance fixed payments. We exclude lease incentives and initial direct costs incurred from our lease payments. Our leases typically do not provide an implicit rate, we use our incremental borrowing rate based on the information available at the commencement date in determining the present value of future payments. For operating leases, after lease commencement, we measure our lease obligation for each period at the present value of any remaining lease payments, discounted by using the rate determined at lease commencement. In our consolidated statement of income, we recognize a single operating lease expense calculated on a straight-line basis over the remaining lease term. The depreciation of the ROU asset increases each year as a result of the declining lease obligation balance. Variable lease payments are not recognized in the measurement of the lease obligation; they are recognized in the period in which the related obligation has been incurred. For finance leases, after lease commencement, we measure our lease obligation by using the effective interest rate method. In each period, the lease obligation will be increased to reflect the interest that is accrued on the related lease obligation by using the appropriate discount rate, offset by a decrease in the lease obligation resulting from the periodic lease payments. We recognize the ROU asset at cost, reduced by any accumulated depreciation. The ROU asset is depreciated on a straight-line basis. Together, the interest expense and depreciation expense result in a front-loaded expense profile. We will present interest expense and depreciation expense separately on our consolidated statements of income. In our consolidated statements of income, we recognize lease expense within general and administrative expense or cost of goods sold depending on the use of the underlying lease. For leases classified as financing, the interest on lease obligations is classified within interest expense. Property and Equipment - Property and equipment are recorded at original cost to us. Upon sale or retirement, the costs and related accumulated depreciation or amortization are eliminated from the respective accounts and any resulting gain or loss is included in income. Maintenance and repairs are charged to expense as incurred. Employee Supplemental Savings Plan Assets - We maintain several non-qualified defined contribution supplemental retirement plans for certain key employees that are accounted for in accordance with ASC 710-10-05, Compensation - General - Deferred Compensation - Rabbi Trust , as the underlying assets are held in rabbi trusts with investments directed by the respective employee. A rabbi trust is a grantor trust generally set up to fund compensation for a select group of management and the assets of this trust are available to satisfy the claims of general creditors in the event of bankruptcy of us. The assets held by the rabbi trusts are recorded at cash surrender value in our consolidated financial statements as Employee supplemental savings plan assets with a related liability to employees recorded as a deferred compensation liability in accrued retirement. Investments - Investments where we have the ability to exercise significant influence, but we do not control, are accounted for under the equity method of accounting and are included in Other assets on our consolidated balance sheets. Significant influence typically exists if we have a 20% to 50% ownership interest in the investee. Under this method of accounting, our share of the net earnings (losses) of the investee is included in Equity in earnings (losses) of unconsolidated subsidiaries on our consolidated statement of income. Investments where we have less than 20% ownership interest in the investee and lack the ability to exercise significant influence are accounted for under ASC 321-10-35, Investments - Equity Securities . Under this topic, our investment equals our cost, less impairment, if any. For investments without a readily determinable fair value, we perform a qualitative assessment to determine if any impairment indicator is present. If an indicator is present, we estimate the fair value to determine if the fair value was less than its carrying value. If the fair value is less than its carrying value or if there is an observable price change through a similar security from the same issuer, we would record an impairment. Deferred Contract Costs - Costs of obtaining or fulfilling a contract that meet the criteria in ASC 340, Other Assets and Deferred Costs , are capitalized and amortized on a systematic basis that is consistent with the transfer of goods or services to the customer. Deferred contract costs are reported on our consolidated balance sheets within current or non-current other assets based on the expected life of the related contract. At December 31, 2020 and 2019, we had $6.6 million and $9.4 million, respectively, of deferred contract costs related to the fulfillment of future contract obligations. For the year ended December 31, 2020 and 2019, we recorded amortization expense of $2.8 million and $2.5 million, respectively. Impairment of Long-Lived Assets - Whenever events or changes in circumstances indicate that the carrying amount of long-lived assets may not be fully recoverable, we evaluate the probability that future undiscounted net cash flows will be less than the carrying amount of the assets. If any impairment were indicated as a result of this review, we would recognize a loss based on the amount by which the carrying amount exceeds the estimated fair value. Contract Liabilities - We receive advances and milestone payments from our customers on selected contracts that exceed revenue earned to date, resulting in contract liabilities. Contract liabilities typically are not considered a significant financing component because it is used to meet working capital demands that can be higher in the early stages of a contract and to protect us from the customer failing to adequately complete some or all of its obligations under the contract. Contract liabilities are reported on our consolidated balance sheet on a net contract basis at the end of each reporting period. Revenue Recognition - We account for a contract when: both we and the customer approve and commit; our rights and those of the customer are identified, payment terms are identified; the contract has commercial substance; and collectability of consideration is probable. At contract inception, we identify the distinct goods or services promised in the contract, referred to as performance obligations. Then we determine the transaction price for the contract; the consideration to which we can expect in exchange for the promised goods or services in the contract. The transaction price can be a fixed or variable amount. It is common for our contracts to contain award fees, incentive fees or other provisions that can either increase or decrease the transaction price. These variable amounts generally are awarded upon achievement of certain performance metrics, program milestones or cost targets and can be based upon customer discretion. We estimate variable consideration at the most likely amount to which we expect to be entitled. We include estimated amounts in the transaction price to the extent it is probable that a significant reversal of cumulative revenue recognized will not occur when the uncertainty associated with the variable consideration is resolved. Our estimates of variable consideration and determination of whether to include estimated amounts in the transaction price are based largely on an assessment of our anticipated performance and historical, current and forecasted information that is reasonably available to us. The transaction price is allocated to each distinct performance obligation using our best estimate of the standalone selling price for each distinct good or service promised in the contract. The primary method used to estimate standalone selling price is the expected cost plus a margin approach, under which we forecast our expected costs of satisfying a performance obligation and then add an appropriate margin for that distinct good or service promised. Revenue is recognized when, or as, the performance obligation is satisfied. We recognize revenue over time when there is a continuous transfer of control to our customer. For our U.S. government contracts, this continuous transfer of control to the customer is supported by clauses in the contract that allow the U.S. government to unilaterally terminate the contract for convenience, pay us for costs incurred plus a reasonable profit and take control of any work in process. When control is transferred over time, revenue is recognized based on the extent of progress towards completion of the performance obligation. Based on the nature of the products and services provided in the contract, we use our judgment to determine if an input measure or output measure best depicts the transfer of control over time. For services contracts, we typically satisfy our performance obligations as services are rendered. We typically use a cost-based input method to measure progress. Contract costs include labor, material and allocable indirect expenses. Revenue is recognized proportionally as contract costs are incurred plus estimated fees. For time-and-material contracts, we bill the customer per labor hour and per material, and revenue is recognized in the amount invoiced since the amount corresponds directly to the value of our performance to date. For stand-ready service contracts, a time-elapsed output method is used to measure progress, and revenue is recognized straight-line over the term of the contract. If a contract does not meet the criteria for recognizing revenue over time, we recognize revenue at a point in time. Revenue is recognized at the point in time when control of the good or service is transferred to our customer. We consider control to transfer when we have a present right to payment and our customer has legal title. Determining a measure of progress and when control transfers requires us to make judgments that affect the timing of when revenue is recognized. Essentially all of our contracts satisfy their performance obligations over time. Contracts are often modified to account for changes in contract specifications and requirements. Contract modifications impact the contract when the modification either creates a new performance obligation or changes the existing enforceable rights and obligations. The effect of a contract modification on the transaction price and our measure of progress for the performance obligation to which it relates is recognized as a cumulative adjustment to revenue and profit. Furthermore, a significant change in one or more estimates could affect the profitability of our contracts. We recognize adjustments in estimated profit on contracts in the period identified. The impact of adjustments in contract estimates can be reflected in either revenue or operating expenses on our consolidated statement of income. We have an Estimate at Completion process in which management reviews the progress and execution of our performance obligations. As part of this process, management reviews information including, but not limited to, any outstanding key contract matters, progress towards completion and the related program schedule, identified risks and opportunities and the related changes in estimates of revenue and costs. The risks and opportunities include management’s judgment about the ability and cost to achieve the contract milestones and other technical contract requirements. Management must make assumptions and estimates regarding labor productivity and availability, the complexity of the work to be performed, the availability of materials, the length of time to complete the performance obligation, execution by our subcontractors, the availability and timing of funding from our customer and overhead cost rates, among other variables. A significant change in one or more of these estimates could affect the profitability of our contracts. For the year ended December 31, 2020, the aggregate impact of adjustments in contract estimates increased our revenue by $10.8 million. No adjustment on any one contract was material to our consolidated financial statements for the year ended December 31, 2020. Contract Costs - Contract costs include direct labor, direct materials, overhead and, when applicable, general and administrative expenses. Incremental costs of obtaining a contract that we expect to recover are recognized as deferred contract costs and are amortized on a systematic basis that is consistent with the transfer to the customer of the goods or services. Other incremental costs are expensed when incurred. Costs of fulfilling a contract that relate directly to a contract or to an anticipated contract that can be specifically identified, generate or enhance resources that will be used in satisfying future performance obligations and are expected to be recovered, are recognized as deferred contract costs and amortized on a systematic basis that is consistent with the transfer of the goods or services to the customer. Other costs of fulfilling a contract (costs of wasted materials, labor or other resources to fulfill the contracts that were not reflected in the price of the contract and costs that relate to satisfied performance obligations in the contract) are expensed when incurred. General and Administrative Expenses - General and administrative expenses include the salaries and wages, plus associated fringe benefits of our employees not performing work directly for customers, and associated facilities costs. Among the functions covered by these costs are corporate business development, bid and proposal, contracts administration, finance and accounting, legal, corporate governance and executive and senior management. In addition, we include stock-based compensation, as well as depreciation and amortization expenses related to the general and administrative function. We recognize interest related to unrecognized tax benefits within interest expense and penalties related to unrecognized tax benefits in general and administrative expenses. We classify indirect costs incurred as cost of services and general and administrative expenses in the same manner as such costs are defined in our disclosure statements under U.S. Government Cost Accounting Standards. Depreciation and Amortization Method - Furniture and office equipment are depreciated using the straight-line method with estimated useful lives ranging from one year to seven years. Leasehold improvements are amortized using the straight-line method over the shorter of the asset's useful life or the term of the lease. Stock-based Compensation - We account for stock-based compensation in accordance with ASC 718, Compensation - Stock Compensation , which requires the use of a valuation model to calculate the fair value of stock-based awards. We have elected to use the Black-Scholes-Merton pricing model to determine fair value of stock options on the dates of grant for our stock options. The fair value of stock options is recognized as operating expenses or is capitalized, as appropriate, straight-line over the period in which service is provided in exchange for the award. The grant date fair value of the restricted stock is equal to the closing market price of our common stock on the date of grant. The compensation expense for restricted stock is recognized over the service period and is based on the grant date fair value of the shares. The grant date fair value of the restricted stock unit (RSU) is equal to the closing market price of our common stock on the grant date less the present value of dividends expected to be awarded during the service period. We recognize the grant date fair value of RSUs of shares we expect to issue as compensation expense ratably over the requisite service period. We account for forfeitures as they occur. Income Taxes - We account for income taxes in accordance with ASC 740, Income Taxes . Under this method, deferred income taxes are determined based on the estimated future tax effects of differences between the financial statement and tax bases of assets and liabilities given the provisions of enacted tax laws. Deferred income tax provisions and benefits are based on changes to the assets or liabilities from year-to-year. In providing for deferred taxes, we consider tax regulations of the jurisdictions in which we operate, estimates of future taxable income and available tax planning strategies. If tax regulations, operating results or the ability to implement tax-planning strategies vary, adjustments to the carrying value of deferred tax assets and liabilities may be required. Valuation allowances are recorded related to deferred tax assets based on the “more likely than not” criteria. We recognize the financial statement benefit of a tax position only after determining that the relevant tax authority would “more likely than not” sustain the position following an audit. For tax positions meeting the “more likely than not” threshold, the amount recognized in the financial statements is the largest benefit that has a greater than 50% likelihood of being realized upon ultimate settlement with the relevant tax authority. Foreign-Currency Translation - All assets and liabilities of foreign subsidiaries are translated into U.S. dollars at fiscal year-end exchange rates. Income and expense items are translated at average monthly exchange rates prevailing during the fiscal year. The resulting translation adjustments are recorded as a component of accumulated other comprehensive income (loss). Comprehensive Income (Loss) - Comprehensive income (loss) consists of net income; translation adjustments, net of tax; and actuarial gain (loss) on defined benefit pension plan, net of tax. Recently Adopted ASUs ASUs adopted during the year ended December 31, 2020 did not have a material impact on our consolidated financial statements. Recently Issued But Not Yet Adopted ASUs ASUs effective after December 31, 2020 are not expected to have a material effect on our consolidated financial statements.

Revenue from Contract with Cust

Revenue from Contract with Customers (Notes)	12 Months Ended
	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Revenue from Contract with Customer [Text Block]	Revenue from Contracts with Customers We derive revenue from contracts with customers primarily from contracts with the U.S. government in the areas of defense, intelligence, homeland security and other federal civilian agencies. Substantially all of our revenue is derived from services and solutions provided to the U.S. government or to prime contractors supporting the U.S. government, including services by our employees and our subcontractors, and solutions that include third-party hardware and software that we purchase and integrate as a part of our overall solutions. Customer requirements may vary from period-to-period depending on the contract. We provide our services and solutions under three types of contracts: cost-reimbursable, fixed-price and time-and-materials. Under cost-reimbursable contracts, we are reimbursed for costs that are determined to be reasonable, allowable and allocable to the contract and paid a fee representing the profit margin negotiated between us and the contracting agency, which may be fixed or performance based. Under fixed-price contracts, we perform specific tasks for a fixed price. Fixed-price contracts may include either a product delivery or specific service performance over a defined period. Under time-and-materials contracts, we are reimbursed for labor at fixed hourly rates and generally reimbursed separately for allowable materials, costs and expenses at cost. We have one reportable segment. Our U.S. government customers typically exercise independent decision-making and contracting authority. Offices or divisions within an agency or department of the U.S. government may directly, or through a prime contractor, use our services as a separate customer as long as the customer has independent decision-making and contracting authority within its organization. We treat sales to U.S. government customers as sales within the U.S. regardless of where the services are performed. We generated 99%, 99% and 98% from revenue generated in the U.S. for the years ended December 31, 2020, 2019 and 2018, respectively. The following tables disclose revenue (in thousands) by contract type, customer and prime or subcontractor for the periods presented. Year Ended 2020 2019 2018 Cost-reimbursable $ 1,724,056 $ 1,541,687 $ 1,325,024 Fixed-price 485,847 451,312 435,599 Time-and-materials 308,481 229,560 197,934 $ 2,518,384 $ 2,222,559 $ 1,958,557 Year Ended 2020 2019 2018 U.S. Government $ 2,476,655 $ 2,175,734 $ 1,913,461 State agencies, international agencies and commercial entities 41,729 46,825 45,096 $ 2,518,384 $ 2,222,559 $ 1,958,557 Year Ended 2020 2019 2018 Prime contractor $ 2,297,452 $ 1,995,471 $ 1,742,097 Subcontractor 220,932 227,088 216,460 $ 2,518,384 $ 2,222,559 $ 1,958,557 We deliver a broad array of IT and technical services solutions under contracts with the U.S. government, state and local governments and commercial customers. The components of receivables are as follows (in thousands): December 31, 2020 December 31, 2019 Billed receivables $ 312,991 $ 311,061 Unbilled receivables 106,007 99,493 Allowance for doubtful accounts (18,377) (11,578) Receivables-net $ 400,621 $ 398,976 Receivables at December 31, 2020 are expected to be substantially collected within one year except for approximately $1.9 million, of which a majority is related to U.S. government receivables. We do not believe that we have significant exposure to credit risk as billed receivable and unbilled receivables are primarily due from the U.S. government. The allowance for doubtful accounts represents our estimate for exposure to compliance, contractual issues and bad debts related to prime contractors. We measure future expected credit losses expected to occur over the estimated life or remaining contractual life of an asset (which includes losses that may be incurred in future periods). When we identify receivables with unique risk characteristics, we evaluate such receivables on an individual basis. A change in our assessment of the creditworthiness of a prime contractor on one of our contracts resulted in an increase in allowance for doubtful accounts during 2020. The following table discloses contract liabilities (in thousands): December 31, 2020 December 31, 2019 Contract liabilities $ 37,218 $ 27,620 Changes in the balance of contract liabilities are primarily due to the timing difference between our performance and our customers' payments. For the year ended December 31, 2020, the amount of revenue that was included in the opening contract liabilities balance was $22.5 million. The remaining performance obligation at December 31, 2020 was $2.8 billion. The following table discloses when we expect to recognize the remaining performance obligation as revenue (in billions): For the year ending December 31, 2021 December 31, 2022 Thereafter $ 2.0 $ 0.3 $ 0.5

Leases (Notes)

Leases (Notes)	12 Months Ended
	Dec. 31, 2020
Leases [Abstract]
Leases of Lessee Disclosure	Leases We elected to adopt ASC 842 using the modified retrospective method at the beginning of the period of adoption, January 1, 2019, through the recognition of a lease obligation and corresponding right of use asset. We elected the following transition related practical expedients: not to reassess whether any expired or existing contracts are or contain leases, not to reassess lease classification as determined under ASC 840, Leases, and, not to reassess initial direct costs for any existing lease. We have also elected not to apply the recognition and measurement requirements to short-term leases (less than 1 year). Prior to the adoption of ASC 842, we accounted for leases under the requirements of ASC 840. Office space and equipment rent expense totaled approximately $39.9 million for the year ended December 31, 2018. The amounts for years prior to the adoption on January 1, 2019 have not been adjusted under the modified retrospective method. Our operating leases are primarily made up of real estate. Our variable lease payments do not depend on an index or a rate or are not in substance fixed payments. Our leases have remaining lease terms of 1 month to 10 years, some of which include options to extend the leases for up to 14 years, and some of which include options to terminate the leases within 1 year. Our transportation vehicles and equipment leases include a residual value guarantee, which is a guarantee made to the lessor that the value of the underlying asset returned to the lessor at the end of the lease will be at least a specific amount. We sublease some of our real estate space. Sublease income is immaterial and is presented net with the corresponding lease expense. We recognize payments related to short-term leases (less than one year) as expense on a straight-line basis over the lease term and variable lease payments in the period in which the obligation for those payments were incurred. As such, our short-term lease expense for the year ended December 31, 2020 and 2019 was $6.3 million and $5.4 million, respectively. For the year ended December 31, 2020 and 2019, we incurred variable lease costs of $2.7 million and $2.4 million, respectively. The balance sheet information related to our leases was as follows (dollars in thousands): December 31, 2020 December 31, 2019 Operating Leases Operating lease right of use assets $ 94,825 $ 117,728 Operating lease obligations—current $ 30,105 $ 29,047 Operating lease obligations—long term $ 80,242 $ 103,148 Finance Leases Property and equipment—gross $ 705 $ 641 Accumulated depreciation (330) (206) Property and equipment—net $ 375 $ 435 Accrued expenses and other current liabilities $ 178 $ 142 Other long-term liabilities $ 227 $ 297 The components of lease expense were as follows (in thousands): For the year ended 2020 2019 Operating lease expenses $ 33,873 $ 33,622 Finance Leases Depreciation of right of use assets $ 168 $ 147 Interest on lease liabilities $ 36 $ 44 The weighted average information related to leases was as follows: December 31, 2020 December 31, 2019 Weighted Average Remaining Lease Term Operating leases 4 years 5 years Finance leases 3 years 3 years Weighted Average Discount Rate Operating leases 4 % 3 % Finance leases 4 % 5 % Future minimum lease payments under non-cancellable leases as of December 31, 2020 were as follows (in thousands): For the year ended: Operating Leases Financing Leases December 31, 2021 $ 33,220 $ 182 December 31, 2022 32,731 176 December 31, 2023 27,090 61 December 31, 2024 14,174 11 December 31, 2025 4,063 12 Thereafter 7,033 1 Total future minimum lease payments 118,311 443 Less imputed interest (7,964) (38) Total $ 110,347 $ 405

Acquisitions (Notes)

Acquisitions (Notes)	12 Months Ended
	Dec. 31, 2020
Business Combinations [Abstract]
Acquisitions	Acquisitions Tapestry Technologies (Tapestry) —On December 11, 2020, we completed the acquisition of Tapestry through a share purchase agreement by and among ManTech International Corporation, Tapestry Technologies, Inc., Project Tribune Holdings, Inc. (Holdco), and all of the shareholders of the Holdco. Tapestry provides unique insight and cybersecurity solutions to the U.S. Defense Information Systems Agency (DISA) and the Department of Defense (DoD). This acquisition broadens our footprint with DISA, serves as a springboard into the broader Defense Department IT marketspace, and provides us access to well-funded DISA and DoD programs. The acquisition was accounted for as a business combination. The results of Tapestry's operations have been included in our consolidated financial statements since that date. We funded the acquisition with cash on hand and borrowing under our revolving credit facility. The preliminary purchase price was $46.3 million and it includes an estimated working capital adjustment. The preliminary purchase price was preliminarily allocated to the underlying assets and liabilities based on their estimated fair value at the date of acquisition. The excess of the purchase price over the fair value of assets acquired and liabilities assumed was recorded as goodwill. As we are still in the process of reviewing the fair value of the assets acquired and liabilities assumed, the purchase price allocation for Tapestry is not complete as of December 31, 2020. In accordance with ASC 805, Business Combinations , we expect to finalize our purchase price allocation within one year of the acquisition date. Recognition of goodwill is largely attributed to the value paid for Tapestry's capabilities, which will broaden our footprint within DISA and the Defense Department IT marketplace. The goodwill recorded for this transaction will be deductible for tax purposes over 15 years. The components of other intangible assets associated with the acquisition were customer relationships and backlog valued at $15.1 million and $1.4 million, respectively. The fair values of the customer relationships and backlog were determined using the excess earnings method (income approach) in which the value is derived from an estimation of the after-tax cash flows specifically attributable to backlog and customer relationships. Assumptions used in the analysis included revenue and expense forecasts, contributory asset charges, tax amortization benefit and discount rates. Customer contracts and related relationships represent the underlying relationships and agreements with Tapestry's existing customers. Customer relationships are amortized using the pattern of benefits method over their estimated useful lives of approximately 20 years. Backlog is amortized using the pattern of benefits method over its estimated useful life of 2 years. The weighted-average amortization period of other intangibles is 18 years. The following table represents the preliminary purchase price allocation for Tapestry (in thousands): Cash and cash equivalents $ 37 Receivables 3,614 Prepaid expenses 225 Goodwill 27,196 Other intangible assets 16,500 Property and equipment 269 Operating lease right of use assets 934 Other assets 10 Accounts payable (483) Accrued salaries and related expenses (1,142) Operating lease obligations—current (457) Operating lease obligations—long term (453) Net assets acquired and liabilities assumed $ 46,250 For the year ended December 31, 2020, we incurred approximately $0.1 million of acquisition costs related to the Tapestry transaction, which are included in general and administrative expenses in our consolidated statement of income. Minerva Engineering (Minerva) —On November 9, 2020, we completed the acquisition of Minerva through a membership interest purchase agreement by and among ManTech International Corporation., Minerva Engineering, LLC and NH Holdco LLC. Minerva is a leading provider of advanced cyber services that support the intelligence community, including risk and vulnerability assessment, incident response and cyber intrusion detection, and wireless signal discovery. This acquisition enhances and expands our cyber defense capabilities within the intelligence community, adding new customers, new past performance qualifications, mission-critical contracts, and highly skilled, cleared professionals that increase our deep cyber security talent base. The acquisition was accounted for as a business combination. The results of Minerva's operations have been included in our consolidated financial statements since that date. We paid for the acquisition with cash on November 9, 2020 and a short-term promissory note that was paid on November 12, 2020. The preliminary purchase price was $32.6 million and it includes an estimated working capital adjustment. The preliminary purchase price was preliminarily allocated to the underlying assets and liabilities based on their estimated fair value at the date of acquisition. The excess of the purchase price over the fair value of assets acquired and liabilities assumed was recorded as goodwill. As we are still in the process of reviewing the fair value of the assets acquired and liabilities assumed, the purchase price allocation for Minerva is not complete as of December 31, 2020. In accordance with ASC 805, Business Combinations , we expect to finalize our purchase price allocation within one year of the acquisition date. Recognition of goodwill is largely attributed to the value paid for Minerva's capabilities, which will broaden our footprint within the intelligence community through the addition of differentiated capabilities and access to new customers and contracts. The goodwill recorded for this transaction will be deductible for tax purposes over 15 years. The components of other intangible assets associated with the acquisition were customer relationships and backlog valued at $10.5 million and $1.1 million, respectively. The fair values of the customer relationships and backlog were determined using the excess earnings method (income approach) in which the value is derived from an estimation of the after-tax cash flows specifically attributable to backlog and customer relationships. Assumptions used in the analysis included revenue and expense forecasts, contributory asset charges, tax amortization benefit and discount rates. Customer contracts and related relationships represent the underlying relationships and agreements with Minerva's existing customers. Customer relationships are amortized using the pattern of benefits method over their estimated useful lives of approximately 20 years. Backlog is amortized using the pattern of benefits method over its estimated useful life of 2 years. The weighted-average amortization period for other intangible assets is 18 years. The following table represents the preliminary purchase price allocation for Minerva (in thousands): Cash and cash equivalents $ 56 Receivables 4,573 Prepaid expenses 25 Goodwill 19,428 Other intangible assets 11,600 Property and equipment 148 Operating lease right of use assets 968 Other assets 29 Accounts payable (1,870) Accrued salaries and related expenses (847) Contract liabilities (449) Operating lease obligations—current (384) Accrued expenses and other current liabilities (141) Operating lease obligations—long term (562) Net assets acquired and liabilities assumed $ 32,574 For the year ended December 31, 2020, we incurred approximately $0.4 million of acquisition costs related to the Minerva transaction, which are included in general and administrative expenses in our consolidated statement of income. H2M Group (H2M) —On August 8, 2019, we completed the acquisition of H2M through a membership interest purchase agreement by and among H2M Group, HHM Holding LLC, and the Members and ManTech International Corporation. H2M is a provider of intelligence and analysis services and solutions primarily to the National Geospatial-Intelligence Agency (NGA). This acquisition strengthens our ability to help key government agencies implement new automation techniques that enable intelligence analysts to more efficiently navigate large amounts of data and distill critical information to inform actionable intelligence and make mission-critical decisions. The acquisition was accounted for as a business combination. The results of H2M's operations have been included in our consolidated financial statements since that date. We funded the acquisition with cash on hand and borrowings on our revolving credit facility. The purchase price of $38.5 million, which includes the finalized working capital adjustment, was allocated to the underlying assets and liabilities based on their estimated fair value at the date of acquisition. The excess of the purchase price over the fair value of assets acquired and liabilities assumed was recorded as goodwill. The purchase price allocation for H2M is complete as of December 31, 2020. Determining the fair value of assets acquired and liabilities assumed requires significant judgment, which includes, among other factors, analysis of historical performance and estimates of future performance of H2M's contracts. In some cases, we have used discounted cash flow analyses, which were based on our best estimate of future revenue, earnings and cash flows as well as our discount rate adjusted for risk. Recognition of goodwill is largely attributed to the value paid for H2M's capabilities to support government agencies in the implementation of high-quality geospatial and professional services. The goodwill recorded for this transaction will be deductible for tax purposes over 15 years. The components of other intangible assets associated with the acquisition were customer relationships and backlog valued at $9.6 million and $2.3 million, respectively. The fair values of the customer relationships and backlog were determined using the excess earnings method (income approach) in which the value is derived from an estimation of the after-tax cash flows specifically attributable to backlog and customer relationships. Assumptions used in the analysis included revenue and expense forecasts, contributory asset charges, tax amortization benefit and discount rates. Customer contracts and related relationships represent the underlying relationships and agreements with H2M's existing customers. Customer relationships are amortized using the pattern of benefits method over their estimated useful lives of approximately 20 years. Backlog is amortized using the pattern of benefits method over its estimated useful life of 2 years. The weighted-average amortization period for other intangible assets is 17 years. The following table represents the finalized purchase price allocation for H2M (in thousands): Cash and cash equivalents $ 29 Receivables 4,187 Prepaid expenses 188 Other current assets 5 Goodwill 25,089 Other intangible assets 11,900 Property and equipment 56 Operating lease right of use assets 152 Other assets 7 Accounts payable (1,956) Accrued salaries and related expenses (1,023) Operating lease obligations—long term (152) Net assets acquired and liabilities assumed $ 38,482 For the year ended December 31, 2019, we incurred approximately $0.3 million of acquisition costs related to the H2M transaction, which are included in general and administrative expenses in our consolidated statement of income. Kforce Government Solutions (KGS) —On April 1, 2019, we completed the acquisition of KGS. KGS was a wholly owned subsidiary of the publicly traded commercial technology and staffing company KForce, Inc. The acquisition was completed through an equity purchase agreement dated February 28, 2019, by and among Kforce Government Solutions, Inc and other beneficiaries and ManTech International Corporation. KGS provides services, IT solutions, transformation and management consulting and data analytics - most notably in the healthcare IT market. This acquisition expands our presence with important customers such as the Department of Veteran Affairs (VA). The acquisition was accounted for as a business combination. The results of KGS's operations have been included in our consolidated financial statements since that date. We funded the acquisition with cash on hand and borrowings on our revolving credit facility. The purchase price of $114.6 million, which includes the finalized working capital adjustment, was allocated to the underlying assets and liabilities based on their estimated fair value at the date of acquisition. The excess of the purchase price over the fair value of assets acquired and liabilities assumed was recorded as goodwill. The purchase price allocation of KGS is complete as of December 31, 2019. Determining the fair value of assets acquired and liabilities assumed requires significant judgment, which includes, among other factors, analysis of historical performance and estimates of future performance of KGS’s contracts. In some cases, we have used discounted cash flow analyses, which were based on our best estimate of future revenue, earnings and cash flows as well as our discount rate adjusted for risk. Recognition of goodwill is largely attributed to the value paid for KGS's capabilities to support customers in IT solutions, transformation and management consulting and data analytics. A majority of the goodwill recorded will not be deductible for tax purposes. The components of other intangible assets associated with the acquisition were customer relationships and backlog valued at $33.1 million and $1.6 million, respectively. The fair values of the customer relationships and backlog were determined using the excess earnings method (income approach) in which the value is derived from an estimation of the after-tax cash flows specifically attributable to backlog and customer relationships. Assumptions used in the analysis included revenue and expense forecasts, contributory asset charges, tax amortization benefit and discount rates. Customer contracts and related relationships represent the underlying relationships and agreements with KGS's existing customers. Customer relationships are amortized using the pattern of benefits method over their estimated useful lives of approximately 20 years. Backlog is amortized straight-line over its estimated useful life of 1 year. The weighted-average amortization period for other intangible assets is 19 years. The following table represents the finalized purchase price allocation for KGS (in thousands): Cash and cash equivalents $ 154 Receivables 17,071 Prepaid expenses 368 Other current assets 168 Goodwill 80,374 Other intangible assets 34,839 Property and equipment 361 Accounts payable (5,035) Accrued salaries and related expenses (4,421) Accrued expenses and other current liabilities (1,860) Deferred income taxes (7,087) Other long-term liabilities (379) Net assets acquired and liabilities assumed $ 114,553 For the year ended December 31, 2019, we incurred approximately $0.9 million of acquisition costs related to the KGS transaction, which are included in general and administrative expenses in our consolidated statement of income.

Earnings per Share (Notes)

Earnings per Share (Notes)	12 Months Ended
	Dec. 31, 2020
Earnings Per Share [Abstract]
Earnings Per Share [Text Block]	Earnings per Share Under ASC 260, Earnings per Share , the two-class method is an earnings allocation formula that determines earnings per share for each class of common stock according to dividends declared (or accumulated) and participation rights in undistributed earnings. Under that method, basic and diluted earnings per share data are presented for each class of common stock. In applying the two-class method, we determined that undistributed earnings should be allocated equally on a per share basis between Class A and Class B common stock. Under our Certificate of Incorporation, the holders of the common stock are entitled to participate ratably, on a share-for-share basis as if all shares of common stock were of a single class, in such dividends, as may be declared by the Board of Directors. During the years ended December 31, 2020, 2019 and 2018, we declared and paid quarterly dividends, in the amount of $0.32, $0.27 and $0.25 per share on both classes of common stock. Basic earnings per share has been computed by dividing net income available to common stockholders by the weighted average number of shares of common stock outstanding during each period. Shares issued during the period and shares reacquired during the period are weighted for the portion of the period in which the shares were outstanding. Diluted earnings per share have been computed in a manner consistent with that of basic earnings per share while giving effect to all potentially dilutive common shares that were outstanding during each period. The net income available to common stockholders and weighted average number of common shares outstanding used to compute basic and diluted earnings per share for each class of common stock are as follows (in thousands, except per share amounts): Year Ended 2020 2019 2018 Distributed earnings $ 51,621 $ 43,207 $ 39,627 Undistributed earnings 68,909 70,683 42,470 Net income $ 120,530 $ 113,890 $ 82,097 Class A common stock: Basic net income available to common stockholders $ 81,087 $ 76,294 $ 54,715 Basic weighted average common shares outstanding 27,105 26,763 26,354 Basic earnings per share $ 2.99 $ 2.85 $ 2.08 Diluted net income available to common stockholders $ 81,405 $ 76,555 $ 54,937 Effect of potential exercise of stock options 328 279 324 Diluted weighted average common shares outstanding 27,433 27,042 26,678 Diluted earnings per share $ 2.97 $ 2.83 $ 2.06 Class B common stock: Basic net income available to common stockholders $ 39,443 $ 37,596 $ 27,382 Basic weighted average common shares outstanding 13,185 13,188 13,189 Basic earnings per share $ 2.99 $ 2.85 $ 2.08 Diluted net income available to common stockholders $ 39,125 $ 37,335 $ 27,160 Diluted weighted average common shares outstanding 13,185 13,188 13,189 Diluted earnings per share $ 2.97 $ 2.83 $ 2.06 For the years ended December 31, 2020, 2019 and 2018, options to purchase 213,248 shares, 288,133 shares and 293,898 shares, respectively, were outstanding but not included in the computation of diluted earnings per share because the options' effect would have been anti-dilutive. For the years ended December 31, 2020, 2019 and 2018, there were 223,405 shares, 338,748 shares and 420,524 shares, respectively, issued from the exercise of stock options.

Property and Equipment (Notes)

Property and Equipment (Notes)	12 Months Ended
	Dec. 31, 2020
Property, Plant and Equipment [Abstract]
Property and Equipment [Text Block]	Property and Equipment Major classes of property and equipment are summarized as follows (in thousands): December 31, 2020 2019 Furniture and equipment $ 194,470 $ 150,640 Leasehold improvements 62,293 49,625 Finance leases 705 641 Property and equipment-gross 257,468 200,906 Accumulated depreciation and amortization (136,172) (115,275) Property and equipment-net $ 121,296 $ 85,631

Goodwill and Other Intangible A

Goodwill and Other Intangible Assets (Notes)	12 Months Ended
	Dec. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets [Text Block]	Goodwill and Other Intangible Assets The changes in the carrying amounts of goodwill during fiscal years 2020 and 2019 were as follows (in thousands): Goodwill Balance Goodwill at December 31, 2018 $ 1,085,806 Acquisitions 105,453 Goodwill at December 31, 2019 1,191,259 Acquisitions 46,624 Acquisition fair value adjustment 11 Goodwill at December 31, 2020 $ 1,237,894 Other intangible assets consisted of the following (in thousands): December 31, 2020 December 31, 2019 Gross Carrying Amount Accumulated Amortization Net Carrying Amount Gross Carrying Amount Accumulated Amortization Net Carrying Amount Other intangible assets: Contract and program intangible assets $ 430,632 $ 242,194 $ 188,438 $ 402,532 $ 221,437 $ 181,095 Capitalized software 54,605 40,812 13,793 52,411 36,728 15,683 Total other intangible assets-net $ 485,237 $ 283,006 $ 202,231 $ 454,943 $ 258,165 $ 196,778 Amortization expense relating to intangible assets for the years ended December 31, 2020, 2019 and 2018 was $27.6 million, $25.4 million and $26.3 million, respectively. Amortization expense for the year ended December 31, 2020 includes an impairment of $1.4 million for capitalized software. We estimate that we will have the following amortization expense for the future periods indicated below (in thousands): Year ending: December 31, 2021 $ 24,581 December 31, 2022 $ 24,232 December 31, 2023 $ 19,612 December 31, 2024 $ 17,486 December 31, 2025 $ 15,423

Debt (Notes)

Debt (Notes)	12 Months Ended
	Dec. 31, 2020
Debt Disclosure [Abstract]
Debt [Text Block]	Debt Revolving Credit Facility - We maintain a credit agreement with a syndicate of lenders led by Bank of America, N.A., as sole administrative agent. The credit agreement provides for a $500 million revolving credit facility, with a $75 million letter of credit sublimit and a $30 million swing line loan sublimit. The credit agreement also includes an accordion feature that permits us to arrange with the lenders for the provision of additional commitments. The maturity date is August 17, 2022. Borrowings under our credit agreement are collateralized by substantially all of our assets and our Material Subsidiaries (as defined in the credit agreement) and bear interest at one of the following variable rates as selected by us at the time of borrowing: a LIBOR based rate plus market spreads (1.25% to 2.25% based on our consolidated total leverage ratio) or Bank of America's base rate plus market spreads (0.25% to 1.25% based on our consolidated total leverage ratio). The aggregate annual weighted average interest rates were 2.32% and 4.11% for the years ended December 31, 2020 and 2019, respectively. The terms of the credit agreement permit prepayment and termination of the loan commitments at any time, subject to certain conditions. The credit agreement requires us to comply with specified financial covenants, including the maintenance of certain leverage ratios and a certain consolidated coverage ratio. The credit agreement also contains various covenants, including affirmative covenants with respect to certain reporting requirements and maintaining certain business activities, and negative covenants that, among other things, may limit or impose restrictions on our ability to incur liens, incur additional indebtedness, make investments, make acquisitions and undertake certain other actions. As of, and during the fiscal years ending, December 31, 2020 and 2019 , we were in compliance with our financial covenants under the credit agreement. There was $15.0 million and $36.5 million outstanding on our revolving credit facility at December 31, 2020 and 2019, respectively. The weighted average borrowings under the revolving portion of the facility during the years ended December 31, 2020 and 2019 were $37.3 million and $37.0 million, respectively. The maximum available borrowing under the revolving credit facility at December 31, 2020 was $478.8 million. At December 31, 2020 and 2019, we had $6.2 million and $5.8 million, respectively, outstanding on our letter of credit that reduces our availability to borrow under our revolving credit facility.

Commitments and Contingencies (

Commitments and Contingencies (Notes)	12 Months Ended
	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies [Text Block]	Commitments and Contingencies Contracts with the U.S. government, including subcontracts, are subject to extensive legal and regulatory requirements and, from time-to-time, agencies of the U.S. government, in the ordinary course of business, investigate whether our operations are conducted in accordance with these requirements and the terms of the relevant contracts. U.S. government investigations of us, whether related to our U.S. government contracts or conducted for other reasons, could result in administrative, civil, or criminal liabilities, including repayments, fines or penalties being imposed upon us, or could lead to suspension or debarment from future U.S. government contracting activities. Management believes it has adequately reserved for any losses that may be experienced from any investigation of which it is aware. The Defense Contract Audit Agency has completed our incurred cost audits through 2016 with no material adjustments. The remaining audits for 2017 through 2020 are not expected to have a material effect on our financial position, results of operations or cash flow and management believes it has adequately reserved for any losses. In the normal course of business, we are involved in certain governmental and legal proceedings, claims and disputes and have litigation pending under several suits. We believe that the ultimate resolution of these matters will not have a material effect on our financial position, results of operations or cash flows, except for the matter noted below. We have $6.2 million outstanding on our letter of credit, of which $5.7 million is related to an outstanding performance bond in connection with a contract between ManTech MENA, LLC and Jadwalean International Operations and Management Company to fulfill technical support requirements for the Royal Saudi Air Force.

Stockholders Equity and Stock-B

Stockholders Equity and Stock-Based Compensation (Notes)	12 Months Ended
	Dec. 31, 2020
Stockholders Equity and Stock-Based Compensation [Abstract]
Stockholders Equity and Stock-Based Compensation [Text Block]	Stockholders' Equity and Stock-Based Compensation Common Stock - We have 150,000,000 shares of authorized Class A common stock, par value $0.01 per share. We have 50,000,000 shares of authorized Class B common stock, par value $0.01 per share. On December 31, 2020, there were 27,294,361 shares of Class A common stock outstanding, 244,113 shares of Class A common stock recorded as treasury stock and 13,176,695 shares of Class B common stock outstanding. Holders of Class A common stock are entitled to one vote for each share held of record and holders of Class B common stock are entitled to ten votes for each share held of record, except with respect to any “going private transaction” (generally, a transaction in which George J. Pedersen (our Chairman Emertius), his affiliates, his direct and indirect permitted transferees or a group, generally including Mr. Pedersen, such affiliates and permitted transferees, seek to buy all outstanding shares), as to which each share of Class A common stock and Class B common stock are entitled to one vote per share. The Class A common stock and the Class B common stock vote together as a single class on all matters submitted to a vote of stockholders, including the election of directors, except as required by law. Holders of common stock do not have cumulative voting rights in the election of directors. Stockholders are entitled to receive, when and if declared by the Board of Directors from time-to-time, such dividends and other distributions in cash, stock or property from our assets or funds legally and contractually available for such purposes subject to any dividend preferences that may be attributable to preferred stock that may be authorized. Each share of Class A common stock and Class B common stock is equal in respect to dividends and other distributions in cash, stock or property, except that in the case of stock dividends, only shares of Class A common stock will be distributed with respect to the Class A common stock and only shares of Class B common stock will be distributed with respect to Class B common stock. In no event will either Class A common stock or Class B common stock be split, divided or combined unless the other class is proportionately split, divided or combined. The shares of Class A common stock are not convertible into any other series or class of securities. Each share of Class B common stock, however, is freely convertible into one share of Class A common stock at the option of the Class B stockholder. Upon the death of Mr. Pedersen, all outstanding shares of Class B common stock automatically convert to Class A common stock. Preferred Stock - We are authorized to issue an aggregate of 20,000,000 shares of preferred stock, $0.01 par value per share, the terms and conditions of which are determined by our Board of Directors upon issuance. The rights, preferences and privileges of holders of our common stock are subject to, and may be adversely affected by, the rights of holders of any shares of preferred stock that we may designate and issue in the future. At December 31, 2020 and 2019, no shares of preferred stock were outstanding and the Board of Directors currently has no plans to issue a series of preferred stock. Accounting for Stock-Based Compensation: Our 2016 Management Incentive Plan (the Plan) was designed to attract, retain and motivate key employees. The types of awards available under the Plan include stock options, restricted stock and RSUs, among others. Equity awards granted under the Plan are settled in shares of Class A common stock. At the beginning of each year, the Plan provides that the number of shares available for issuance automatically increases by an amount equal to 1.5% of the total number of shares of Class A and Class B common stock outstanding on December 31st of the previous year. On January 2, 2021, there were 607,066 additional shares made available for issuance under the Plan. Through December 31, 2020, the Board of Directors has authorized the issuance of up to 15,751,005 shares under this Plan. Through December 31, 2020, the remaining aggregate number of shares of our common stock available for future grants under the Plan was 7,160,951. The Plan expires in March 2026. The Plan is administered by the Compensation Committee of our Board of Directors, along with its delegates. Subject to the express provisions of the Plan, the Committee has the Board of Directors' authority to administer and interpret the Plan, including the discretion to determine the exercise price, vesting schedule, contractual life and the number of shares to be issued. Stock Compensation Expense - For the years ended December 31, 2020, 2019 and 2018, we recorded $11.4 million, $7.5 million and $5.1 million of stock-based compensation expense, respectively. No compensation expense of employees with stock awards was capitalized during the years ended December 31, 2020, 2019 and 2018. For the year ended December 31, 2020, 2019 and 2018 we recorded $1.6 million, $2.1 million and $3.4 million, respectively, to income tax benefit related to the exercise of stock options, vested cancellations and the vesting of restricted stock and restricted stock units. Stock Options - Under the Plan, we have issued stock options. A stock option granted gives the holder the right, but not the obligation to purchase a certain number of shares at a predetermined price for a specific period of time. We typically issue options that vest over 3 years in equal installments beginning on the first anniversary of the date of grant. Under the terms of the Plan, the contractual life of the option grants may not exceed 8 years. During the years ended December 31, 2019 and 2018, we issued options that expire 5 years from the date of grant. There were no options granted during the year ended December 31, 2020. Fair Value Determination - We have used the Black-Scholes-Merton option pricing model to determine fair value of our stock option awards on the date of grant. We will reconsider the use of the Black-Scholes-Merton model if additional information becomes available in the future that indicates another model would be more appropriate or if grants issued in future periods have characteristics that cannot be reasonably estimated under this model. The following weighted-average assumptions were used for option grants during the years ended December 31, 2019 and 2018: • Volatility - The expected volatility of the options granted was estimated based upon historical volatility of our share price through weekly observations of our trading history. • Expected life of options - The expected life of options granted to employees was determined from historical exercises of the grantee population. The options had graded vesting over 3 years in equal installments beginning on the first anniversary of the date of the grant and a contractual term of 5 years. • Risk-free interest rate - The yield on zero-coupon U.S. Treasury strips was used to extrapolate a forward-yield curve. This “term structure” of future interest rates was then input into a numeric model to provide the equivalent risk-free rate to be used in the Black-Scholes-Merton model based on the expected term of the underlying grants. • Dividend yield - The Black-Scholes-Merton valuation model requires an expected dividend yield as an input. For the years ended December 31, 2019 and 2018, we have calculated our expected dividend yield based on an expected annual cash dividend of $1.08 per share and $1.00 per share, respectively. The following table summarizes weighted-average assumptions used in our calculations of fair value for the years ended December 31, 2019 and 2018: Year Ended December 31, 2019 2018 Volatility 27.21 % 26.57 % Expected life of options 3 years 3 years Risk-free interest rate 1.98 % 2.72 % Dividend yield 1.76 % 2.00 % Stock Option Activity - There were no options granted during the year ended December 31, 2020. The weighted-average fair value of options granted during the years ended December 31, 2019 and 2018, as determined under the Black-Scholes-Merton valuation model, was $12.07 and $10.42, respectively. Option grants that vested during the years ended December 31, 2020, 2019 and 2018 had a combined fair value of $3.6 million, $2.5 million and $1.5 million, respectively. The following table summarizes stock option activity for the years ended December 31, 2020, 2019 and 2018: Number of Shares Weighted Average Exercise Price Aggregate Intrinsic Value Weighted Average Remaining Contractual Life Stock options outstanding at December 31, 2017 1,169,408 $ 35.88 $ 16,731 Granted 466,828 $ 54.87 Exercised (420,524) $ 30.05 $ 12,411 Cancelled and expired (122,312) $ 43.85 Stock options outstanding at December 31, 2018 1,093,400 $ 45.34 $ 8,776 Granted 489,947 $ 63.87 Exercised (338,748) $ 37.94 $ 9,641 Cancelled and expired (108,504) $ 51.21 Stock options outstanding at December 31, 2019 1,136,095 $ 54.98 $ 28,291 Exercised (223,405) $ 46.72 $ 6,897 Cancelled and expired (126,863) $ 61.17 Stock options outstanding at December 31, 2020 785,827 $ 56.33 $ 25,629 3 years Stock options exercisable at December 31, 2020 432,184 $ 52.05 $ 15,944 2 years The following table summarizes non-vested stock options for the year ended December 31, 2020: Number of Shares Weighted Average Fair Value Non-vested stock options at December 31, 2019 845,555 $ 10.88 Vested (368,592) $ 9.88 Cancelled (123,320) $ 11.63 Non-vested stock options at December 31, 2020 353,643 $ 11.66 Unrecognized compensation expense related to outstanding stock options was $3.0 million as of December 31, 2020, which is expected to be recognized over a weighted-average period of one year and will be adjusted for forfeitures as they occur. Restricted Stock - Under the Plan, we have issued restricted stock. A restricted stock award is an issuance of shares that cannot be sold or transferred by the recipient until the vesting period lapses. Restricted stock issued to members of our Board of Directors vest in one year. The related compensation expense is recognized over the service period and is based on the grant date fair value of the stock and the number of shares expected to vest. The grant date fair value of the restricted stock is equal to the closing market price of our common stock on the date of grant. Restricted Stock Activity - The following table summarizes the restricted stock activity during the years ended December 31, 2020 and 2019: Number of Shares Weighted Average Fair Value Non-vested restricted stock at December 31, 2018 20,000 $ 52.83 Granted 24,000 $ 62.66 Vested (20,000) $ 52.83 Non-vested restricted stock at December 31, 2019 24,000 $ 62.66 Granted 24,000 $ 71.11 Vested (24,000) $ 62.66 Non-vested restricted stock at December 31, 2020 24,000 $ 71.11 RSUs - Under the Plan, we issued performance-based and time-based RSUs. RSUs are not actual shares, but rather a right to receive shares in the future. The shares are not issued and the employee cannot sell or transfer shares prior to vesting and has no voting rights until the RSUs vest. Employees who are granted RSUs do not receive dividend payments during the vesting period. The employees' performance-based RSUs will result in the delivery of shares if (a) performance criteria is met and (b) the employee remains employed, in good standing, through the date of the performance period of two years. The employees' time-based RSUs will result in the delivery of shares in one-third increments on the first, second and third anniversaries of the date of grant. Shares are issued net of applicable payroll tax withholdings. The grant date fair value of the RSUs is equal to the closing market price of our common stock on the grant date less the present value of dividends expected to be awarded during the service period. We recognize the grant date fair value of RSUs of shares we expect to issue as compensation expense ratably over the requisite service period. RSU Activity - The following table summarizes the RSU activity during the years ended December 31, 2020 and 2019: Number of Units Weighted Average Fair Value RSUs at December 31, 2018 137,596 $ 45.11 Granted 145,440 $ 59.43 Vested (60,915) $ 42.75 Forfeited (11,294) $ 51.88 RSUs at December 31, 2019 210,827 $ 55.31 Granted 266,880 $ 68.83 Vested (73,047) $ 53.85 Forfeited (57,861) $ 64.52 RSUs at December 31, 2020 346,799 $ 64.48

Retirement Plans (Notes)

Retirement Plans (Notes)	12 Months Ended
	Dec. 31, 2020
Retirement Benefits [Abstract]
Retirement Plans [Text Block]	Retirement Plans As of December 31, 2020, we maintained a qualified defined contribution plan. Our qualified defined contribution plan covers substantially all employees and complies with Section 401 of the Internal Revenue Code. Under this plan, we stipulated a basic matching contribution that matches a portion of the participants' contribution based upon a defined schedule. Additionally, this plan contains a discretionary contribution component where we may contribute additional amounts based on a percentage of eligible employees' compensation. Contributions are invested by an independent investment company. The choice of investment alternatives is at the election of each participating employee. Our contributions to the plan were approximately $33.0 million, $26.7 million and $23.5 million for the years ended December 31, 2020, 2019 and 2018, respectively. As of December 31, 2020, we maintained an Employee Supplemental Savings Plan (ESSP), which is a nonqualified deferred compensation plan for certain key employees. Prior to January 1, 2020, eligible employees could defer up to 75% of qualified annual base compensation and 100% of bonus. Effective for the 2020 plan year, additional deferrals have been suspended. Contributions made in 2020 relate to deferrals on bonuses earned in 2019 but paid in 2020. In the ESSP, participant deferral accounts are credited with a rate of return based on investment elections as selected by the participant. The assets related to the ESSP are held in a rabbi trust owned by us for benefit of the participating employees. The trust investments are in the form of variable universal life insurance products, which are owned by us. These investments seek to replicate the return of the participant investment elections. Employee contributions to this plan were approximately $0.5 million, $3.4 million and $3.4 million for the years ended December 31, 2020, 2019 and 2018, respectively. We maintained a nonqualified supplemental defined benefit pension plan for certain retired employees of an acquired company as of December 31, 2020. These plans were informally and partially funded beginning in 1999 through a rabbi trust. Assets held in a rabbi trust are not eligible to be included in the calculation of plan status. At both December 31, 2020 and 2019, 100% of the rabbi trust assets were invested in a money market account with a commercial bank. All covered employees retired prior to 1998. Our benefit obligation was $0.7 million and $0.7 million at December 31, 2020 and 2019, respectively.

Income Taxes (Notes)

Income Taxes (Notes)	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Income Taxes [Text Block]	Income Taxes The domestic and foreign components of income operations before income taxes and equity method investments were as follows (in thousands): Year Ended 2020 2019 2018 Domestic $ 156,496 $ 136,164 $ 110,514 Foreign (99) (66) 91 Income from operations before income taxes and equity method investments $ 156,397 $ 136,098 $ 110,605 The provision for income taxes was comprised of the following components (in thousands): Year Ended 2020 2019 2018 Federal $ 16,296 $ (9,092) $ 11,602 State 7,463 6,015 4,937 Foreign 140 97 133 Current provision (benefit) 23,899 (2,980) 16,672 Federal 8,183 13,451 8,010 State 1,710 2,301 3,586 Deferred provision 9,893 15,752 11,596 Federal 1,996 9,440 234 State 87 — 28 Foreign (10) — — Non-current provision resulting from allocating tax benefits directly to changes in liabilities 2,073 9,440 262 Provision for income taxes $ 35,865 $ 22,212 $ 28,530 The schedule of effective income tax rate reconciliation is as follows: Year Ended 2020 2019 2018 Statutory U.S. Federal tax rate 21.0 % 21.0 % 21.0 % Increase (decrease) in tax rate resulting from: State taxes—net of Federal benefit 4.9 % 4.8 % 6.1 % Research and development credit (1.8) % (8.8) % — % Stock-based compensation (0.9) % (1.3) % (2.2) % ESSP (0.7) % (1.0) % 0.4 % Excess executive compensation 0.7 % 0.8 % 0.8 % Other, net (0.3) % 0.8 % (0.3) % Effective tax rate 22.9 % 16.3 % 25.8 % We paid income taxes, net of refunds of $23.9 million for the year ended December 31, 2020. We paid income taxes, net of refunds of $21.4 million for the years ended December 31, 2019. We received an income tax refund, net of payments of $4.3 million for the years ended December 31, 2018. Deferred income taxes arise from temporary differences between the tax basis of assets and liabilities and their reported amounts in the financial statements. A summary of the tax effect of the significant components of deferred income taxes is as follows (in thousands): December 31, 2020 2019 Goodwill and other intangibles $ 152,412 $ 136,882 Lease arrangements 25,863 31,128 Property and equipment 17,237 13,270 Unbilled receivables - IRC Section 481(a) 2,946 5,878 Gross deferred tax liabilities 198,458 187,158 Lease obligations (28,652) (34,146) Retirement and other liabilities (23,071) (18,614) Allowance for potential contract losses and other contract reserves (4,815) (2,205) Foreign and state operating loss carryforwards (2,253) (2,239) Less: Valuation allowance 1,971 1,828 Gross deferred tax assets (56,820) (55,376) Net deferred tax liabilities $ 141,638 $ 131,782 At December 31, 2020, we had state and foreign net operating losses of approximately $9.5 million and $1.7 million, respectively. The state net operating losses expire beginning 2027 through 2039. We recorded a full valuation allowance against the foreign net operating losses and a partial valuation allowance against the state net operating losses, as we do not believe those losses will be fully utilized in the future. A reconciliation of the beginning and ending balances of the total amounts of gross unrecognized tax benefits is as follows (in thousands): December 31, 2020 2019 2018 Gross unrecognized tax benefits at beginning of year $ 9,635 $ 490 $ 220 Increases in tax positions for current year 1,712 1,839 320 Increases in tax positions for prior years 371 7,718 36 Lapse in statute of limitations (10) — (86) Decreases in tax positions for prior years — (412) — Gross unrecognized tax benefits at end of year $ 11,708 $ 9,635 $ 490 The total liability for gross unrecognized tax benefits as of December 31, 2020, 2019 and 2018 includes $11.7 million, $9.6 million and $0.4 million, respectively, of unrecognized net tax benefits which, if ultimately recognized, would reduce our annual effective tax rate in a future period. These liabilities, along with liabilities for interest and penalties, are included in accounts payable and accrued expenses and Other long-term liabilities in our consolidated balance sheet. Interest, which is included in Interest expense in our consolidated statement of income, was not material for all years presented. During the year ended December 31, 2020, we recognized an increase in unrecognized tax benefits of approximately $2.1 million of which $1.8 million related to an increase in research and development tax credits available to us. During the year ended December 31, 2019 we recognized an increase in unrecognized tax benefits related to available research and development credits of $7.7 million for tax years 2016-2018 and $1.8 million for the 2019 tax year. We are subject to income taxes in the U.S., various state and foreign jurisdictions. Tax statutes and regulations within each jurisdiction are subject to interpretation and require significant judgment to apply. We are no longer subject to U.S. federal or non-U.S. income tax examinations by tax authorities for the years before 2016. We are currently under examination by the Internal Revenue Services and various state tax authorities for tax years 2016-2018. We are no longer subject to U.S. state tax examinations by tax authorities for the years before 2015. Given the inherent uncertainty surrounding the on-going IRS

Quarterly Financial Information

Quarterly Financial Information (Unaudited) (Notes)	12 Months Ended
	Dec. 31, 2020
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Information (Unaudited) [Text Block]	Quarterly Financial Information (Unaudited) The quarterly financial data reflects, in our opinion, all normal and recurring adjustments to present fairly the results of operations for such periods. Results of any one or more quarters are not necessarily indicative of annual results or continuing trends. The following tables set forth selected unaudited quarterly financial data: 2020 March 31, June 30, September 30, December 31, (in thousands, except per share data) Revenues $ 610,912 $ 632,492 $ 636,196 $ 638,784 Operating income $ 38,898 $ 39,586 $ 39,341 $ 40,224 Income from operations before income taxes and equity method investments $ 38,271 $ 39,091 $ 39,042 $ 39,993 Net income $ 28,679 $ 29,948 $ 29,739 $ 32,164 Class A common stock: Basic weighted average common shares outstanding 26,992 27,082 27,139 27,207 Basic earnings per share $ 0.71 $ 0.74 $ 0.74 $ 0.80 Diluted weighted average common shares outstanding 27,367 27,409 27,413 27,528 Diluted earnings per share $ 0.71 $ 0.74 $ 0.73 $ 0.79 Class B common stock: Basic weighted average common shares outstanding 13,187 13,187 13,187 13,177 Basic earnings per share $ 0.71 $ 0.74 $ 0.74 $ 0.80 Diluted weighted average common shares outstanding 13,187 13,187 13,187 13,177 Diluted earnings per share $ 0.71 $ 0.74 $ 0.73 $ 0.79 2019 March 31, June 30, September 30, December 31, (in thousands, except per share data) Revenues $ 501,930 $ 537,037 $ 579,179 $ 604,413 Operating income $ 28,532 $ 33,297 $ 38,402 $ 38,094 Income from operations before income taxes and equity method investments $ 28,196 $ 32,504 $ 37,794 $ 37,604 Net income $ 21,118 $ 24,214 $ 27,937 $ 40,621 Class A common stock: Basic weighted average common shares outstanding 26,584 26,707 26,822 26,933 Basic earnings per share $ 0.53 $ 0.61 $ 0.70 $ 1.01 Diluted weighted average common shares outstanding 26,819 26,936 27,128 27,279 Diluted earnings per share $ 0.53 $ 0.60 $ 0.69 $ 1.00 Class B common stock: Basic weighted average common shares outstanding 13,188 13,188 13,188 13,188 Basic earnings per share $ 0.53 $ 0.61 $ 0.70 $ 1.01 Diluted weighted average common shares outstanding 13,188 13,188 13,188 13,188 Diluted earnings per share $ 0.53 $ 0.60 $ 0.69 $ 1.00

Schedule II

Schedule II	12 Months Ended
	Dec. 31, 2020
SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract]
Valuation and Qualifying Accounts	SCHEDULE II Valuation and Qualifying Accounts Activities in our allowance accounts for the years ended December 31, 2020, 2019 and 2018 were as follows (in thousands): Doubtful Accounts Balance at Beginning of Period Charged to Costs and Expenses Deductions Other* Balance at End of Period 2018 $ 6,157 — — 76 $ 6,233 2019 $ 6,233 3,000 — 2,345 $ 11,578 2020 $ 11,578 5,244 — 1,555 $ 18,377 * Other represents doubtful account reserves released or recorded as part of net revenues for estimated customer disallowances. Deferred Tax Asset Valuation Balance at Beginning of Period Charged to Costs and Expenses Deductions Other Balance at End of Period 2018 $ 717 820 — — $ 1,537 2019 $ 1,537 291 — — $ 1,828 2020 $ 1,828 143 — — $ 1,971

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Principles of Consolidation [Policy Text Block]	Principles of Consolidation - Our consolidated financial statements include the accounts of ManTech International Corporation, subsidiaries we control and variable interest entities that are required to be consolidated. All intercompany accounts and transactions have been eliminated.
Use of Accounting Estimates [Policy Text Block]	Use of Accounting Estimates - We prepare our consolidated financial statements in conformity with U.S. GAAP, which requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. These estimates involve judgments with respect to, among other things, various future economic factors that are difficult to predict and are beyond our control. Therefore, actual amounts could differ from these estimates.
Business Combinations Policy [Policy Text Block]	Business Combinations - The accounting for our business combinations consists of allocating the purchase price to tangible and intangible assets acquired and liabilities assumed based on their estimated fair values, with the excess recorded as goodwill. We have up to one year from the acquisition date to use information as of each acquisition date to adjust the fair value of the acquired assets and liabilities, which may result in material changes to their recorded values with an offsetting adjustment to goodwill. Determining the fair value of assets acquired and liabilities assumed requires significant judgment, which includes, among other factors, analysis of historical performance and estimates of future performance. In some cases, we have used discounted cash flow analyses, which were based on our best estimate of future revenue, earnings and cash flows as well as our discount rate, adjusted for risk, and estimated attrition rates.
Fair Value of Financial Instruments [Policy Text Block]	Fair Value of Financial Instruments - The carrying value of our cash and cash equivalents, accounts receivable, accounts payable and accrued expenses approximate their fair value because of the short-term nature of these amounts.
Cash and Cash Equivalents [Policy Text Block]	Cash and Cash Equivalents - For the purpose of reporting cash flows, cash and cash equivalents include cash on hand, amounts due from banks and short-term investments with maturity dates of three months or less at the date of purchase.
Contract Assets [Policy Test Block]	Contract Assets - Amounts are invoiced as work progresses in accordance with agreed-upon contractual terms, either at periodic intervals or upon achievement of contractual milestones. Generally, revenue recognition occurs before billing, resulting in contract assets. These contract assets are referred to as unbilled receivables and are reported within receivables, net on our consolidated balance sheet.
Billed Receivables [Policy Text Block]	Billed Receivables - Amounts billed and due from our customers are classified as billed receivables and are reported within receivables, net on the consolidated balance sheet. The portion of the payments retained by the customer until final contract settlement is not considered a significant financing component because the intent is to protect the customer.
Goodwill [Policy Text Block]	Goodwill - The purchase price of an acquired business is allocated to the tangible assets, financial assets and separately recognized intangible assets acquired less liabilities assumed based upon their respective fair values, with the excess recorded as goodwill. We review goodwill at least annually for impairment, or whenever events or circumstances indicate that the carrying value of long-lived assets may not be fully recoverable. We have elected to perform this annual review as of October 31 st of each calendar year. In reviewing goodwill for impairment, we have the option to first assess qualitative factors to determine whether the existence of events or circumstances leads to a determination that it is more likely than not that the estimated fair value of a reporting unit is less than its carrying amount. If we elect to perform a qualitative assessment and determine that it is more likely than not that the fair value of the reporting unit is less than its carry amount, then we will perform the quantitative impairment test (described below). We also may bypass the qualitative assessment for any reporting unit in any period and, proceed directly to perform the quantitative impairment test. The quantitative goodwill impairment test, is used to identify both the existence of impairment and the amount of the impairment loss, compares the fair value of a reporting unit with its carrying amount, including goodwill. If the fair value of a reporting unit exceeds its carrying amount, the goodwill of the reporting unit is not impaired. If the carrying amount of a reporting unit exceeds its fair value, an impairment loss will be recognized in the amount equal to that excess, limited to the total amount of goodwill allocated to that reporting unit.
Other Intangible Assets [Policy Text Block]	Other Intangible Assets - Contract rights and other intangible assets are amortized primarily using the pattern of benefits method over periods ranging from 1 year to 25 years. We account for the cost of computer software developed or obtained for internal use in accordance with Accounting Standards Codification (ASC) 350-985, Intangibles - Goodwill and Other - Software . These capitalized software costs are included in other intangible assets, net. We account for software development costs related to software products for sale, lease or otherwise marketed in accordance with ASC 985-20, Software - Costs of Software to Be Sold, Leased, or Marketed
Lessee, Leases [Policy Text Block]	Leases - We adopted ASC 842, Leases , on January 1, 2019. We elected to apply the provisions of the standard as of the date of adoption, and, therefore, have not restated prior comparative periods. Upon adoption, we recorded operating lease obligations of $129.6 million and operating lease right of use (ROU) assets of $118.7 million. We elected the practical expedient to recognize the lease payments related to short-term leases as profit or loss on a straight-line basis over the lease term and variable lease payments in the period in which the obligation for those payments are incurred. We also elected the following transition related practical expedients: not to reassess whether expired or existing contracts are or contain leases, not to reassess lease classification as determined under ASC 840 and not to reassess initial direct costs from any existing lease. We elected the practical expedient as an accounting election not to separate nonlease components from lease components on all classes of underlying assets. Our leases include nonlease components such as common area maintenance, utilities and operating expenses. Additionally, we implemented internal controls and key system functionality to enable the preparation of financial information upon adoption. ASC 842 had a material impact on our consolidated balance sheet, but did not have an impact on our consolidated income statement. The most significant impact was the recognition of ROU assets and lease obligations for operating leases, while our accounting for finance leases remained substantially unchanged. We determine whether a contract is or contains a lease at inception. A contract is or contains a lease if the contract conveys the right to control the use of identified property or equipment (an identified asset) for a period of time in exchange for consideration. We have the right to control the use of the identified asset when we have both of the following: the right to obtain substantially all of the economic benefits from use of the identified asset and the right to direct the use of the identified asset. In making this determination, we consider all relevant facts and circumstances. We reassess whether a contract is or contains a lease only if the terms and conditions of the contract are changed. We account for lease components and nonlease components associated with a lease as a single lease component. Operating leases are included in Operating lease right of use assets, Operating lease obligations—current and Operating lease obligations—long term on our consolidated balance sheets. Finance leases are included in Property and equipment—net, Accrued expenses and other current liabilities and Other long-term liabilities on our consolidated balance sheets. Our ROU asset is recognized as the lease obligation, any initial direct costs and any prepaid lease payments, less any lease incentives. Our lease obligations are recognized based on the present value of the future minimum lease payments over the lease term at commencement date. Our lease payments consist of amounts relating to the use of the underlying asset during the lease term, specifically fixed payments, payments to be made in optional periods when we are reasonably certain to exercise an option to extend the lease or not to exercise an option to terminate the lease and the amounts probable of being owed by us under residual guarantees. Our variable lease payments are excluded in measuring ROU assets and lease obligations because they do not depend on an index or a rate or are not in substance fixed payments. We exclude lease incentives and initial direct costs incurred from our lease payments. Our leases typically do not provide an implicit rate, we use our incremental borrowing rate based on the information available at the commencement date in determining the present value of future payments. For operating leases, after lease commencement, we measure our lease obligation for each period at the present value of any remaining lease payments, discounted by using the rate determined at lease commencement. In our consolidated statement of income, we recognize a single operating lease expense calculated on a straight-line basis over the remaining lease term. The depreciation of the ROU asset increases each year as a result of the declining lease obligation balance. Variable lease payments are not recognized in the measurement of the lease obligation; they are recognized in the period in which the related obligation has been incurred. For finance leases, after lease commencement, we measure our lease obligation by using the effective interest rate method. In each period, the lease obligation will be increased to reflect the interest that is accrued on the related lease obligation by using the appropriate discount rate, offset by a decrease in the lease obligation resulting from the periodic lease payments. We recognize the ROU asset at cost, reduced by any accumulated depreciation. The ROU asset is depreciated on a straight-line basis. Together, the interest expense and depreciation expense result in a front-loaded expense profile. We will present interest expense and depreciation expense separately on our consolidated statements of income. In our consolidated statements of income, we recognize lease expense within general and administrative expense or cost of goods sold depending on the use of the underlying lease. For leases classified as financing, the interest on lease obligations is classified within interest expense.
Property and Equipment [Policy Text Block]	Property and Equipment - Property and equipment are recorded at original cost to us. Upon sale or retirement, the costs and related accumulated depreciation or amortization are eliminated from the respective accounts and any resulting gain or loss is included in income. Maintenance and repairs are charged to expense as incurred.
Employee Supplemental Savings Plan Assets [Policy Text Block]	Employee Supplemental Savings Plan Assets - We maintain several non-qualified defined contribution supplemental retirement plans for certain key employees that are accounted for in accordance with ASC 710-10-05, Compensation - General - Deferred Compensation - Rabbi Trust
Investments [Policy Text Block]	Investments - Investments where we have the ability to exercise significant influence, but we do not control, are accounted for under the equity method of accounting and are included in Other assets on our consolidated balance sheets. Significant influence typically exists if we have a 20% to 50% ownership interest in the investee. Under this method of accounting, our share of the net earnings (losses) of the investee is included in Equity in earnings (losses) of unconsolidated subsidiaries on our consolidated statement of income. Investments where we have less than 20% ownership interest in the investee and lack the ability to exercise significant influence are accounted for under ASC 321-10-35, Investments - Equity Securities . Under this topic, our investment equals our cost, less impairment, if any. For investments without a readily determinable fair value, we perform a qualitative assessment to determine if any impairment indicator is present. If an indicator is present, we estimate the fair value to determine if the fair value was less than its carrying value. If the fair value is less than its carrying value or if there is an observable price change through a similar security from the same issuer, we would record an impairment.
Deferred Contract Costs [Policy Text Block]	Deferred Contract Costs - Costs of obtaining or fulfilling a contract that meet the criteria in ASC 340, Other Assets and Deferred Costs
Impairment of Long-Lived Assets [Policy Text Block]	Impairment of Long-Lived Assets - Whenever events or changes in circumstances indicate that the carrying amount of long-lived assets may not be fully recoverable, we evaluate the probability that future undiscounted net cash flows will be less than the carrying amount of the assets. If any impairment were indicated as a result of this review, we would recognize a loss based on the amount by which the carrying amount exceeds the estimated fair value.
Contract Liabilities [Policy Text Block]	Contract Liabilities - We receive advances and milestone payments from our customers on selected contracts that exceed revenue earned to date, resulting in contract liabilities. Contract liabilities typically are not considered a significant financing component because it is used to meet working capital demands that can be higher in the early stages of a contract and to protect us from the customer failing to adequately complete some or all of its obligations under the contract. Contract liabilities are reported on our consolidated balance sheet on a net contract basis at the end of each reporting period.
Revenue Recognition [Policy Text Block]	Revenue Recognition - We account for a contract when: both we and the customer approve and commit; our rights and those of the customer are identified, payment terms are identified; the contract has commercial substance; and collectability of consideration is probable. At contract inception, we identify the distinct goods or services promised in the contract, referred to as performance obligations. Then we determine the transaction price for the contract; the consideration to which we can expect in exchange for the promised goods or services in the contract. The transaction price can be a fixed or variable amount. It is common for our contracts to contain award fees, incentive fees or other provisions that can either increase or decrease the transaction price. These variable amounts generally are awarded upon achievement of certain performance metrics, program milestones or cost targets and can be based upon customer discretion. We estimate variable consideration at the most likely amount to which we expect to be entitled. We include estimated amounts in the transaction price to the extent it is probable that a significant reversal of cumulative revenue recognized will not occur when the uncertainty associated with the variable consideration is resolved. Our estimates of variable consideration and determination of whether to include estimated amounts in the transaction price are based largely on an assessment of our anticipated performance and historical, current and forecasted information that is reasonably available to us. The transaction price is allocated to each distinct performance obligation using our best estimate of the standalone selling price for each distinct good or service promised in the contract. The primary method used to estimate standalone selling price is the expected cost plus a margin approach, under which we forecast our expected costs of satisfying a performance obligation and then add an appropriate margin for that distinct good or service promised. Revenue is recognized when, or as, the performance obligation is satisfied. We recognize revenue over time when there is a continuous transfer of control to our customer. For our U.S. government contracts, this continuous transfer of control to the customer is supported by clauses in the contract that allow the U.S. government to unilaterally terminate the contract for convenience, pay us for costs incurred plus a reasonable profit and take control of any work in process. When control is transferred over time, revenue is recognized based on the extent of progress towards completion of the performance obligation. Based on the nature of the products and services provided in the contract, we use our judgment to determine if an input measure or output measure best depicts the transfer of control over time. For services contracts, we typically satisfy our performance obligations as services are rendered. We typically use a cost-based input method to measure progress. Contract costs include labor, material and allocable indirect expenses. Revenue is recognized proportionally as contract costs are incurred plus estimated fees. For time-and-material contracts, we bill the customer per labor hour and per material, and revenue is recognized in the amount invoiced since the amount corresponds directly to the value of our performance to date. For stand-ready service contracts, a time-elapsed output method is used to measure progress, and revenue is recognized straight-line over the term of the contract. If a contract does not meet the criteria for recognizing revenue over time, we recognize revenue at a point in time. Revenue is recognized at the point in time when control of the good or service is transferred to our customer. We consider control to transfer when we have a present right to payment and our customer has legal title. Determining a measure of progress and when control transfers requires us to make judgments that affect the timing of when revenue is recognized. Essentially all of our contracts satisfy their performance obligations over time. Contracts are often modified to account for changes in contract specifications and requirements. Contract modifications impact the contract when the modification either creates a new performance obligation or changes the existing enforceable rights and obligations. The effect of a contract modification on the transaction price and our measure of progress for the performance obligation to which it relates is recognized as a cumulative adjustment to revenue and profit. Furthermore, a
Contract Costs [Policy Text Block]	Contract Costs - Contract costs include direct labor, direct materials, overhead and, when applicable, general and administrative expenses. Incremental costs of obtaining a contract that we expect to recover are recognized as deferred contract costs and are amortized on a systematic basis that is consistent with the transfer to the customer of the goods or services. Other incremental costs are expensed when incurred. Costs of fulfilling a contract that relate directly to a contract or to an anticipated contract that can be specifically identified, generate or enhance resources that will be used in satisfying future performance obligations and are expected to be recovered, are recognized as deferred contract costs and amortized on a systematic basis that is consistent with the transfer of the goods or services to the customer. Other costs of fulfilling a contract (costs of wasted materials, labor or other resources to fulfill the contracts that were not reflected in the price of the contract and costs that relate to satisfied performance obligations in the contract) are expensed when incurred.
General and Administrative Expenses [Policy Text Block]	General and Administrative Expenses - General and administrative expenses include the salaries and wages, plus associated fringe benefits of our employees not performing work directly for customers, and associated facilities costs. Among the functions covered by these costs are corporate business development, bid and proposal, contracts administration, finance and accounting, legal, corporate governance and executive and senior management. In addition, we include stock-based compensation, as well as depreciation and amortization expenses related to the general and administrative function. We recognize interest related to unrecognized tax benefits within interest expense and penalties related to unrecognized tax benefits in general and administrative expenses. We classify indirect costs incurred as cost of services and general and administrative expenses in the same manner as such costs are defined in our disclosure statements under U.S. Government Cost Accounting Standards.
Depreciation and Amortization Method [Policy Text Block]	Depreciation and Amortization Method - Furniture and office equipment are depreciated using the straight-line method with estimated useful lives ranging from one year to seven years. Leasehold improvements are amortized using the straight-line method over the shorter of the asset's useful life or the term of the lease.
Stock-based Compensation [Policy Text Block]	Stock-based Compensation - We account for stock-based compensation in accordance with ASC 718, Compensation - Stock Compensation
Income Taxes [Policy Text Block]	Income Taxes - We account for income taxes in accordance with ASC 740, Income Taxes . Under this method, deferred income taxes are determined based on the estimated future tax effects of differences between the financial statement and tax bases of assets and liabilities given the provisions of enacted tax laws. Deferred income tax provisions and benefits are based on changes to the assets or liabilities from year-to-year. In providing for deferred taxes, we consider tax regulations of the jurisdictions in which we operate, estimates of future taxable income and available tax planning strategies. If tax regulations, operating results or the ability to implement tax-planning strategies vary, adjustments to the carrying value of deferred tax assets and liabilities may be required. Valuation allowances are recorded related to deferred tax assets based on the “more
Foreign-Currency Translation [Policy Text Block]	Foreign-Currency Translation - All assets and liabilities of foreign subsidiaries are translated into U.S. dollars at fiscal year-end exchange rates. Income and expense items are translated at average monthly exchange rates prevailing during the fiscal year. The resulting translation adjustments are recorded as a component of accumulated other comprehensive income (loss).
Comprehensive Income (Loss) [Policy Text Block]	Comprehensive Income (Loss) - Comprehensive income (loss) consists of net income; translation adjustments, net of tax; and actuarial gain (loss) on defined benefit pension plan, net of tax.
Recently Adopted ASUs [Text Block]	Recently Adopted ASUsASUs adopted during the year ended December 31, 2020 did not have a material impact on our consolidated financial statements.
Recently Issued But Not Yet Adopted ASUs [Policy Text Block]	Recently Issued But Not Yet Adopted ASUs ASUs effective after December 31, 2020 are not expected to have a material effect on our consolidated financial statements.

Revenue from Contract with Cu_2

Revenue from Contract with Customers (Tables)	12 Months Ended
	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Revenue by Contract Type [Table Text Block]	Year Ended 2020 2019 2018 Cost-reimbursable $ 1,724,056 $ 1,541,687 $ 1,325,024 Fixed-price 485,847 451,312 435,599 Time-and-materials 308,481 229,560 197,934 $ 2,518,384 $ 2,222,559 $ 1,958,557
Revenue by Customer [Table Text Block]	Year Ended 2020 2019 2018 U.S. Government $ 2,476,655 $ 2,175,734 $ 1,913,461 State agencies, international agencies and commercial entities 41,729 46,825 45,096 $ 2,518,384 $ 2,222,559 $ 1,958,557
Revenue by Contractor Type [Table Text Block]	Year Ended 2020 2019 2018 Prime contractor $ 2,297,452 $ 1,995,471 $ 1,742,097 Subcontractor 220,932 227,088 216,460 $ 2,518,384 $ 2,222,559 $ 1,958,557
Schedule Of Contract Receivables [Table Text Block]	The components of receivables are as follows (in thousands): December 31, 2020 December 31, 2019 Billed receivables $ 312,991 $ 311,061 Unbilled receivables 106,007 99,493 Allowance for doubtful accounts (18,377) (11,578) Receivables-net $ 400,621 $ 398,976
Contract with Customer, Asset and Liability [Table Text Block]	The following table discloses contract liabilities (in thousands): December 31, 2020 December 31, 2019 Contract liabilities $ 37,218 $ 27,620
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table Text Block]	The following table discloses when we expect to recognize the remaining performance obligation as revenue (in billions): For the year ending December 31, 2021 December 31, 2022 Thereafter $ 2.0 $ 0.3 $ 0.5

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2020
Leases [Abstract]
Lessee, Lease, Balance Sheet	The balance sheet information related to our leases was as follows (dollars in thousands): December 31, 2020 December 31, 2019 Operating Leases Operating lease right of use assets $ 94,825 $ 117,728 Operating lease obligations—current $ 30,105 $ 29,047 Operating lease obligations—long term $ 80,242 $ 103,148 Finance Leases Property and equipment—gross $ 705 $ 641 Accumulated depreciation (330) (206) Property and equipment—net $ 375 $ 435 Accrued expenses and other current liabilities $ 178 $ 142 Other long-term liabilities $ 227 $ 297
Lease, Cost [Table Text Block]	The components of lease expense were as follows (in thousands): For the year ended 2020 2019 Operating lease expenses $ 33,873 $ 33,622 Finance Leases Depreciation of right of use assets $ 168 $ 147 Interest on lease liabilities $ 36 $ 44
Lease Weighted Average Information [Table Text Block]	The weighted average information related to leases was as follows: December 31, 2020 December 31, 2019 Weighted Average Remaining Lease Term Operating leases 4 years 5 years Finance leases 3 years 3 years Weighted Average Discount Rate Operating leases 4 % 3 % Finance leases 4 % 5 %
Schedule of Maturities of Lease Liabilities [Table Text Block]	Future minimum lease payments under non-cancellable leases as of December 31, 2020 were as follows (in thousands): For the year ended: Operating Leases Financing Leases December 31, 2021 $ 33,220 $ 182 December 31, 2022 32,731 176 December 31, 2023 27,090 61 December 31, 2024 14,174 11 December 31, 2025 4,063 12 Thereafter 7,033 1 Total future minimum lease payments 118,311 443 Less imputed interest (7,964) (38) Total $ 110,347 $ 405

Acquisitions (Tables)

Acquisitions (Tables)	12 Months Ended
	Dec. 31, 2020
Tapestry Technologies
Business Combination Segment Allocation [Line Items]
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed [Table Text Block]	The following table represents the preliminary purchase price allocation for Tapestry (in thousands): Cash and cash equivalents $ 37 Receivables 3,614 Prepaid expenses 225 Goodwill 27,196 Other intangible assets 16,500 Property and equipment 269 Operating lease right of use assets 934 Other assets 10 Accounts payable (483) Accrued salaries and related expenses (1,142) Operating lease obligations—current (457) Operating lease obligations—long term (453) Net assets acquired and liabilities assumed $ 46,250
Minerva Engineering [Member]
Business Combination Segment Allocation [Line Items]
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed [Table Text Block]	The following table represents the preliminary purchase price allocation for Minerva (in thousands): Cash and cash equivalents $ 56 Receivables 4,573 Prepaid expenses 25 Goodwill 19,428 Other intangible assets 11,600 Property and equipment 148 Operating lease right of use assets 968 Other assets 29 Accounts payable (1,870) Accrued salaries and related expenses (847) Contract liabilities (449) Operating lease obligations—current (384) Accrued expenses and other current liabilities (141) Operating lease obligations—long term (562) Net assets acquired and liabilities assumed $ 32,574
H2M Group [Member]
Business Combination Segment Allocation [Line Items]
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed [Table Text Block]	The following table represents the finalized purchase price allocation for H2M (in thousands): Cash and cash equivalents $ 29 Receivables 4,187 Prepaid expenses 188 Other current assets 5 Goodwill 25,089 Other intangible assets 11,900 Property and equipment 56 Operating lease right of use assets 152 Other assets 7 Accounts payable (1,956) Accrued salaries and related expenses (1,023) Operating lease obligations—long term (152) Net assets acquired and liabilities assumed $ 38,482
Kforce Government Solutions [Member]
Business Combination Segment Allocation [Line Items]
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed [Table Text Block]	The following table represents the finalized purchase price allocation for KGS (in thousands): Cash and cash equivalents $ 154 Receivables 17,071 Prepaid expenses 368 Other current assets 168 Goodwill 80,374 Other intangible assets 34,839 Property and equipment 361 Accounts payable (5,035) Accrued salaries and related expenses (4,421) Accrued expenses and other current liabilities (1,860) Deferred income taxes (7,087) Other long-term liabilities (379) Net assets acquired and liabilities assumed $ 114,553

Earnings per Share (Tables)

Earnings per Share (Tables)	12 Months Ended
	Dec. 31, 2020
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]	The net income available to common stockholders and weighted average number of common shares outstanding used to compute basic and diluted earnings per share for each class of common stock are as follows (in thousands, except per share amounts): Year Ended 2020 2019 2018 Distributed earnings $ 51,621 $ 43,207 $ 39,627 Undistributed earnings 68,909 70,683 42,470 Net income $ 120,530 $ 113,890 $ 82,097 Class A common stock: Basic net income available to common stockholders $ 81,087 $ 76,294 $ 54,715 Basic weighted average common shares outstanding 27,105 26,763 26,354 Basic earnings per share $ 2.99 $ 2.85 $ 2.08 Diluted net income available to common stockholders $ 81,405 $ 76,555 $ 54,937 Effect of potential exercise of stock options 328 279 324 Diluted weighted average common shares outstanding 27,433 27,042 26,678 Diluted earnings per share $ 2.97 $ 2.83 $ 2.06 Class B common stock: Basic net income available to common stockholders $ 39,443 $ 37,596 $ 27,382 Basic weighted average common shares outstanding 13,185 13,188 13,189 Basic earnings per share $ 2.99 $ 2.85 $ 2.08 Diluted net income available to common stockholders $ 39,125 $ 37,335 $ 27,160 Diluted weighted average common shares outstanding 13,185 13,188 13,189 Diluted earnings per share $ 2.97 $ 2.83 $ 2.06

Property and Equipment (Tables)

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2020
Property, Plant and Equipment [Abstract]
Property and Equipment [Table Text Block]	Major classes of property and equipment are summarized as follows (in thousands): December 31, 2020 2019 Furniture and equipment $ 194,470 $ 150,640 Leasehold improvements 62,293 49,625 Finance leases 705 641 Property and equipment-gross 257,468 200,906 Accumulated depreciation and amortization (136,172) (115,275) Property and equipment-net $ 121,296 $ 85,631

Goodwill and Other Intangible_2

Goodwill and Other Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Goodwill [Table Text Block]	The changes in the carrying amounts of goodwill during fiscal years 2020 and 2019 were as follows (in thousands): Goodwill Balance Goodwill at December 31, 2018 $ 1,085,806 Acquisitions 105,453 Goodwill at December 31, 2019 1,191,259 Acquisitions 46,624 Acquisition fair value adjustment 11 Goodwill at December 31, 2020 $ 1,237,894
Schedule of Other Intangible Assets [Table Text Block]	Other intangible assets consisted of the following (in thousands): December 31, 2020 December 31, 2019 Gross Carrying Amount Accumulated Amortization Net Carrying Amount Gross Carrying Amount Accumulated Amortization Net Carrying Amount Other intangible assets: Contract and program intangible assets $ 430,632 $ 242,194 $ 188,438 $ 402,532 $ 221,437 $ 181,095 Capitalized software 54,605 40,812 13,793 52,411 36,728 15,683 Total other intangible assets-net $ 485,237 $ 283,006 $ 202,231 $ 454,943 $ 258,165 $ 196,778
Schedule of Other Intangible Assets, Future Amortization Expense [Table Text Block]	We estimate that we will have the following amortization expense for the future periods indicated below (in thousands): Year ending: December 31, 2021 $ 24,581 December 31, 2022 $ 24,232 December 31, 2023 $ 19,612 December 31, 2024 $ 17,486 December 31, 2025 $ 15,423

Stockholders Equity and Stock_2

Stockholders Equity and Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]	The following table summarizes weighted-average assumptions used in our calculations of fair value for the years ended December 31, 2019 and 2018: Year Ended December 31, 2019 2018 Volatility 27.21 % 26.57 % Expected life of options 3 years 3 years Risk-free interest rate 1.98 % 2.72 % Dividend yield 1.76 % 2.00 %
Share-based Payment Arrangement, Option, Activity [Table Text Block]	The following table summarizes stock option activity for the years ended December 31, 2020, 2019 and 2018: Number of Shares Weighted Average Exercise Price Aggregate Intrinsic Value Weighted Average Remaining Contractual Life Stock options outstanding at December 31, 2017 1,169,408 $ 35.88 $ 16,731 Granted 466,828 $ 54.87 Exercised (420,524) $ 30.05 $ 12,411 Cancelled and expired (122,312) $ 43.85 Stock options outstanding at December 31, 2018 1,093,400 $ 45.34 $ 8,776 Granted 489,947 $ 63.87 Exercised (338,748) $ 37.94 $ 9,641 Cancelled and expired (108,504) $ 51.21 Stock options outstanding at December 31, 2019 1,136,095 $ 54.98 $ 28,291 Exercised (223,405) $ 46.72 $ 6,897 Cancelled and expired (126,863) $ 61.17 Stock options outstanding at December 31, 2020 785,827 $ 56.33 $ 25,629 3 years Stock options exercisable at December 31, 2020 432,184 $ 52.05 $ 15,944 2 years
Schedule of Non-Vested Share Activity [Table Text Block]	The following table summarizes non-vested stock options for the year ended December 31, 2020: Number of Shares Weighted Average Fair Value Non-vested stock options at December 31, 2019 845,555 $ 10.88 Vested (368,592) $ 9.88 Cancelled (123,320) $ 11.63 Non-vested stock options at December 31, 2020 353,643 $ 11.66
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Schedule of Share-based Compensation, Restricted Stock Activity [Table Text Block]	The following table summarizes the restricted stock activity during the years ended December 31, 2020 and 2019: Number of Shares Weighted Average Fair Value Non-vested restricted stock at December 31, 2018 20,000 $ 52.83 Granted 24,000 $ 62.66 Vested (20,000) $ 52.83 Non-vested restricted stock at December 31, 2019 24,000 $ 62.66 Granted 24,000 $ 71.11 Vested (24,000) $ 62.66 Non-vested restricted stock at December 31, 2020 24,000 $ 71.11
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Schedule of Share-based Compensation, Restricted Stock Activity [Table Text Block]	The following table summarizes the RSU activity during the years ended December 31, 2020 and 2019: Number of Units Weighted Average Fair Value RSUs at December 31, 2018 137,596 $ 45.11 Granted 145,440 $ 59.43 Vested (60,915) $ 42.75 Forfeited (11,294) $ 51.88 RSUs at December 31, 2019 210,827 $ 55.31 Granted 266,880 $ 68.83 Vested (73,047) $ 53.85 Forfeited (57,861) $ 64.52 RSUs at December 31, 2020 346,799 $ 64.48

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Schedule of Income before Income Tax, Domestic and Foreign [Table Text Block]	The domestic and foreign components of income operations before income taxes and equity method investments were as follows (in thousands): Year Ended 2020 2019 2018 Domestic $ 156,496 $ 136,164 $ 110,514 Foreign (99) (66) 91 Income from operations before income taxes and equity method investments $ 156,397 $ 136,098 $ 110,605
Schedule of Components of Income Tax Expense (Benefit) [Table Text Block]	The provision for income taxes was comprised of the following components (in thousands): Year Ended 2020 2019 2018 Federal $ 16,296 $ (9,092) $ 11,602 State 7,463 6,015 4,937 Foreign 140 97 133 Current provision (benefit) 23,899 (2,980) 16,672 Federal 8,183 13,451 8,010 State 1,710 2,301 3,586 Deferred provision 9,893 15,752 11,596 Federal 1,996 9,440 234 State 87 — 28 Foreign (10) — — Non-current provision resulting from allocating tax benefits directly to changes in liabilities 2,073 9,440 262 Provision for income taxes $ 35,865 $ 22,212 $ 28,530
Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]	The schedule of effective income tax rate reconciliation is as follows: Year Ended 2020 2019 2018 Statutory U.S. Federal tax rate 21.0 % 21.0 % 21.0 % Increase (decrease) in tax rate resulting from: State taxes—net of Federal benefit 4.9 % 4.8 % 6.1 % Research and development credit (1.8) % (8.8) % — % Stock-based compensation (0.9) % (1.3) % (2.2) % ESSP (0.7) % (1.0) % 0.4 % Excess executive compensation 0.7 % 0.8 % 0.8 % Other, net (0.3) % 0.8 % (0.3) % Effective tax rate 22.9 % 16.3 % 25.8 %
Schedule of Deferred Tax Assets and Liabilities [Table Text Block]	A summary of the tax effect of the significant components of deferred income taxes is as follows (in thousands): December 31, 2020 2019 Goodwill and other intangibles $ 152,412 $ 136,882 Lease arrangements 25,863 31,128 Property and equipment 17,237 13,270 Unbilled receivables - IRC Section 481(a) 2,946 5,878 Gross deferred tax liabilities 198,458 187,158 Lease obligations (28,652) (34,146) Retirement and other liabilities (23,071) (18,614) Allowance for potential contract losses and other contract reserves (4,815) (2,205) Foreign and state operating loss carryforwards (2,253) (2,239) Less: Valuation allowance 1,971 1,828 Gross deferred tax assets (56,820) (55,376) Net deferred tax liabilities $ 141,638 $ 131,782
Schedule of Unrecognized Tax Benefits Roll Forward [Table Text Block]	A reconciliation of the beginning and ending balances of the total amounts of gross unrecognized tax benefits is as follows (in thousands): December 31, 2020 2019 2018 Gross unrecognized tax benefits at beginning of year $ 9,635 $ 490 $ 220 Increases in tax positions for current year 1,712 1,839 320 Increases in tax positions for prior years 371 7,718 36 Lapse in statute of limitations (10) — (86) Decreases in tax positions for prior years — (412) — Gross unrecognized tax benefits at end of year $ 11,708 $ 9,635 $ 490

Quarterly Financial Informati_2

Quarterly Financial Information (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2020
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Information [Table Text Block]	The following tables set forth selected unaudited quarterly financial data: 2020 March 31, June 30, September 30, December 31, (in thousands, except per share data) Revenues $ 610,912 $ 632,492 $ 636,196 $ 638,784 Operating income $ 38,898 $ 39,586 $ 39,341 $ 40,224 Income from operations before income taxes and equity method investments $ 38,271 $ 39,091 $ 39,042 $ 39,993 Net income $ 28,679 $ 29,948 $ 29,739 $ 32,164 Class A common stock: Basic weighted average common shares outstanding 26,992 27,082 27,139 27,207 Basic earnings per share $ 0.71 $ 0.74 $ 0.74 $ 0.80 Diluted weighted average common shares outstanding 27,367 27,409 27,413 27,528 Diluted earnings per share $ 0.71 $ 0.74 $ 0.73 $ 0.79 Class B common stock: Basic weighted average common shares outstanding 13,187 13,187 13,187 13,177 Basic earnings per share $ 0.71 $ 0.74 $ 0.74 $ 0.80 Diluted weighted average common shares outstanding 13,187 13,187 13,187 13,177 Diluted earnings per share $ 0.71 $ 0.74 $ 0.73 $ 0.79 2019 March 31, June 30, September 30, December 31, (in thousands, except per share data) Revenues $ 501,930 $ 537,037 $ 579,179 $ 604,413 Operating income $ 28,532 $ 33,297 $ 38,402 $ 38,094 Income from operations before income taxes and equity method investments $ 28,196 $ 32,504 $ 37,794 $ 37,604 Net income $ 21,118 $ 24,214 $ 27,937 $ 40,621 Class A common stock: Basic weighted average common shares outstanding 26,584 26,707 26,822 26,933 Basic earnings per share $ 0.53 $ 0.61 $ 0.70 $ 1.01 Diluted weighted average common shares outstanding 26,819 26,936 27,128 27,279 Diluted earnings per share $ 0.53 $ 0.60 $ 0.69 $ 1.00 Class B common stock: Basic weighted average common shares outstanding 13,188 13,188 13,188 13,188 Basic earnings per share $ 0.53 $ 0.61 $ 0.70 $ 1.01 Diluted weighted average common shares outstanding 13,188 13,188 13,188 13,188 Diluted earnings per share $ 0.53 $ 0.60 $ 0.69 $ 1.00

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Jan. 01, 2019
Accounting Policies [Line Items]
Operating lease obligations	$ 110,347		$ 129,600
Operating lease right of use assets	94,825	$ 117,728	$ 118,700
Deferred Contract Costs	6,600	9,400
Deferred Contract Cost, Amortization Expense	2,800	$ 2,500
Contract with Customer, Asset, Cumulative Catch-up Adjustment to Revenue, Change in Estimate of Transaction Price	$ 10,800
More Likely Than Not Threshold	50.00%
Minimum [Member]
Accounting Policies [Line Items]
Equity Method Investment, Ownership Percentage	20.00%
Property, Plant and Equipment, Useful Life	1 year
Maximum [Member]
Accounting Policies [Line Items]
Maturity Threshold For Including In Cash And Cash Equivalent	three months
Equity Method Investment, Ownership Percentage	50.00%
Property, Plant and Equipment, Useful Life	7 years
Other Intangible Assets [Member] | Minimum [Member]
Accounting Policies [Line Items]
Finite-Lived Intangible Asset, Useful Life	1 year
Other Intangible Assets [Member] | Maximum [Member]
Accounting Policies [Line Items]
Finite-Lived Intangible Asset, Useful Life	25 years
Software and Software Development Costs [Member]
Accounting Policies [Line Items]
Finite-Lived Intangible Asset, Useful Life	5 years
Less than [Member]
Accounting Policies [Line Items]
Cost Method Investment, Ownership Percentage	20.00%

Revenue from Contract with Cu_3

Revenue from Contract with Customers Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020USD ($)Entities	Dec. 31, 2019	Dec. 31, 2018
Additional Revenue [Line Items]
Number of Reportable Segments | Entities	1
Contract Receivable, Due after Year One	$ 1.9
Contract with Customer, Liability, Revenue Recognized	22.5
Revenue, Remaining Performance Obligation, Amount	$ 2,800
Revenue, Segment Benchmark [Member] | UNITED STATES
Additional Revenue [Line Items]
Concentration Risk, Percentage	99.00%	99.00%	98.00%

Revenue from Contract with Cu_4

Revenue from Contract with Customers Revenue by Contract Type (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenue by Contract Type [Line Items]
Revenues	$ 638,784	$ 636,196	$ 632,492	$ 610,912	$ 604,413	$ 579,179	$ 537,037	$ 501,930	$ 2,518,384	$ 2,222,559	$ 1,958,557
Cost-reimbursable
Revenue by Contract Type [Line Items]
Revenues									1,724,056	1,541,687	1,325,024
Fixed-price
Revenue by Contract Type [Line Items]
Revenues									485,847	451,312	435,599
Time-and-materials
Revenue by Contract Type [Line Items]
Revenues									$ 308,481	$ 229,560	$ 197,934

Revenue from Contract with Cu_5

Revenue from Contract with Customers Revenue by Customer (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenue, Major Customer [Line Items]
Revenues	$ 638,784	$ 636,196	$ 632,492	$ 610,912	$ 604,413	$ 579,179	$ 537,037	$ 501,930	$ 2,518,384	$ 2,222,559	$ 1,958,557
U.S. Government [Member]
Revenue, Major Customer [Line Items]
Revenues									2,476,655	2,175,734	1,913,461
State agencies, international agencies and commercial entities
Revenue, Major Customer [Line Items]
Revenues									$ 41,729	$ 46,825	$ 45,096

Revenue from Contract with Cu_6

Revenue from Contract with Customers Revenue by Contractor Type (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenue by Contract Type [Line Items]
Revenues	$ 638,784	$ 636,196	$ 632,492	$ 610,912	$ 604,413	$ 579,179	$ 537,037	$ 501,930	$ 2,518,384	$ 2,222,559	$ 1,958,557
Prime contractor
Revenue by Contract Type [Line Items]
Revenues									2,297,452	1,995,471	1,742,097
Subcontractor
Revenue by Contract Type [Line Items]
Revenues									$ 220,932	$ 227,088	$ 216,460

Revenue from Contract with Cu_7

Revenue from Contract with Customers Schedule of Contract Receivables (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Revenue from Contract with Customer [Abstract]
Billed receivables	$ 312,991	$ 311,061
Unbilled receivables	106,007	99,493
Allowance for doubtful accounts	(18,377)	(11,578)
Receivables-net	$ 400,621	$ 398,976

Revenue from Contract with Cu_8

Revenue from Contract with Customers Contract with Customer, Asset and Liability (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Revenue from Contract with Customer [Abstract]
Contract liabilities	$ 37,218	$ 27,620

Revenue from Contract with Cu_9

Revenue from Contract with Customers Revenue, Remaining Performance Obligation (Details) $ in Billions	Dec. 31, 2020USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 2.8
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Revenue, Remaining Performance Obligation, Amount	$ 2
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Revenue, Remaining Performance Obligation, Amount	$ 0.3
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period
Revenue, Remaining Performance Obligation, Amount	$ 0.5

Leases Narrative (Details)

Leases Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Operating Leases, Rent Expense, Net			$ 39.9
Short-term Lease, Cost	$ 6.3	$ 5.4
Variable Lease, Cost	$ 2.7	$ 2.4
Minimum [Member]
Lessee Operating And Finance Leases Remaining Lease Term	1 month
Lessee Operating And Finance Lease, Option to Extend	1 year
Maximum [Member]
Lessee Operating And Finance Leases Remaining Lease Term	10 years
Lessee Operating And Finance Lease, Option to Extend	14 years

Leases Balance Sheet Informatio

Leases Balance Sheet Information (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Jan. 01, 2019
Operating Leases [Abstract]
Operating lease right of use assets	$ 94,825	$ 117,728	$ 118,700
Operating lease obligations—current	30,105	29,047
Operating lease obligations—long term	80,242	103,148
Finance Leases [Abstract]
Property and equipment—gross	705	641
Accumulated depreciation	(330)	(206)
Property and equipment—net	375	435
Accrued expenses and other current liabilities	178	142
Other long-term liabilities	$ 227	$ 297

Leases Cost (Details)

Leases Cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Operating lease expenses	$ 33,873	$ 33,622
Finance Leases
Depreciation of right of use assets	168	147
Interest on lease liabilities	$ 36	$ 44

Leases Term and Discount Rate (

Leases Term and Discount Rate (Details)	Dec. 31, 2020	Dec. 31, 2019
Weighted Average Remaining Lease Term [Abstract]
Operating Lease, Weighted Average Remaining Lease Term	4 years	5 years
Finance Lease, Weighted Average Remaining Lease Term	3 years	3 years
Weighted Average Discount Rate [Abstract]
Operating Lease, Weighted Average Discount Rate, Percent	4.00%	3.00%
Finance Lease, Weighted Average Discount Rate, Percent	4.00%	5.00%

Leases Schedule of Maturity of

Leases Schedule of Maturity of Lease Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Jan. 01, 2019
Lessee, Operating Lease, Liability, Payment, Due [Abstract]
December 31, 2021	$ 33,220
December 31, 2022	32,731
December 31, 2023	27,090
December 31, 2024	14,174
December 31, 2025	4,063
Thereafter	7,033
Total future minimum lease payments	118,311
Less imputed interest	(7,964)
Total	110,347	$ 129,600
Finance Lease, Liability, Payment, Due [Abstract]
December 31, 2021	182
December 31, 2022	176
December 31, 2023	61
December 31, 2024	11
December 31, 2025	12
Thereafter	1
Total future minimum lease payments	443
Less imputed interest	(38)
Total	$ 405

Acquisitions (Narrative) (Detai

Acquisitions (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Tapestry Technologies
Business Acquisition [Line Items]
Business Combination, Consideration Transferred	$ 46.3
ExpectedGoodwillTaxAmortizationPeriod	15 years
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	18 years
Business Combination, Separately Recognized Transactions, Additional Disclosures, Acquisition Cost Expensed	$ 0.1
Tapestry Technologies | Customer Relationships [Member]
Business Acquisition [Line Items]
Acquired Finite-lived Intangible Asset, Amount	$ 15.1
Finite-Lived Intangible Asset, Useful Life	20 years
Tapestry Technologies | Backlog [Member]
Business Acquisition [Line Items]
Acquired Finite-lived Intangible Asset, Amount	$ 1.4
Finite-Lived Intangible Asset, Useful Life	2 years
Minerva Engineering [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred	$ 32.6
ExpectedGoodwillTaxAmortizationPeriod	15 years
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	18 years
Business Combination, Separately Recognized Transactions, Additional Disclosures, Acquisition Cost Expensed	$ 0.4
Minerva Engineering [Member] | Customer Relationships [Member]
Business Acquisition [Line Items]
Acquired Finite-lived Intangible Asset, Amount	$ 10.5
Finite-Lived Intangible Asset, Useful Life	20 years
Minerva Engineering [Member] | Backlog [Member]
Business Acquisition [Line Items]
Acquired Finite-lived Intangible Asset, Amount	$ 1.1
Finite-Lived Intangible Asset, Useful Life	2 years
H2M Group [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred	$ 38.5
ExpectedGoodwillTaxAmortizationPeriod	15 years
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	17 years
Business Combination, Separately Recognized Transactions, Additional Disclosures, Acquisition Cost Expensed		$ 0.3
H2M Group [Member] | Customer Relationships [Member]
Business Acquisition [Line Items]
Acquired Finite-lived Intangible Asset, Amount	$ 9.6
Finite-Lived Intangible Asset, Useful Life	20 years
H2M Group [Member] | Backlog [Member]
Business Acquisition [Line Items]
Acquired Finite-lived Intangible Asset, Amount	$ 2.3
Finite-Lived Intangible Asset, Useful Life	2 years
Kforce Government Solutions [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred	$ 114.6
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	19 years
Business Combination, Separately Recognized Transactions, Additional Disclosures, Acquisition Cost Expensed		$ 0.9
Kforce Government Solutions [Member] | Customer Relationships [Member]
Business Acquisition [Line Items]
Acquired Finite-lived Intangible Asset, Amount	$ 33.1
Finite-Lived Intangible Asset, Useful Life	20 years
Kforce Government Solutions [Member] | Backlog [Member]
Business Acquisition [Line Items]
Acquired Finite-lived Intangible Asset, Amount	$ 1.6
Finite-Lived Intangible Asset, Useful Life	1 year

Acquisitions (Schedule of Recog

Acquisitions (Schedule of Recognized Identified Assets Acquired and Liabilities Assumed) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Business Acquisition [Line Items]
Goodwill	$ 1,237,894	$ 1,191,259	$ 1,085,806
Tapestry Technologies
Business Acquisition [Line Items]
Cash and cash equivalents	37
Receivables	3,614
Prepaid expenses	225
Goodwill	27,196
Other intangible assets	16,500
Property and equipment	269
Operating lease right of use assets	934
Other assets	10
Accounts payable	(483)
Accrued salaries and related expenses	(1,142)
Operating lease obligations—current	(457)
Operating lease obligations—long term	(453)
Net assets acquired and liabilities assumed	46,250
Minerva Engineering [Member]
Business Acquisition [Line Items]
Cash and cash equivalents	56
Receivables	4,573
Prepaid expenses	25
Goodwill	19,428
Other intangible assets	11,600
Property and equipment	148
Operating lease right of use assets	968
Other assets	29
Accounts payable	(1,870)
Accrued salaries and related expenses	(847)
Contract liabilities	(449)
Operating lease obligations—current	(384)
Accrued expenses and other current liabilities	(141)
Operating lease obligations—long term	(562)
Net assets acquired and liabilities assumed	32,574
H2M Group [Member]
Business Acquisition [Line Items]
Cash and cash equivalents	29
Receivables	4,187
Prepaid expenses	188
Other current assets	5
Goodwill	25,089
Other intangible assets	11,900
Property and equipment	56
Operating lease right of use assets	152
Other assets	7
Accounts payable	(1,956)
Accrued salaries and related expenses	(1,023)
Operating lease obligations—long term	(152)
Net assets acquired and liabilities assumed	38,482
Kforce Government Solutions [Member]
Business Acquisition [Line Items]
Cash and cash equivalents	154
Receivables	17,071
Prepaid expenses	368
Other current assets	168
Goodwill	80,374
Other intangible assets	34,839
Property and equipment	361
Accounts payable	(5,035)
Accrued salaries and related expenses	(4,421)
Accrued expenses and other current liabilities	(1,860)
Deferred income taxes	(7,087)
Other long-term liabilities	(379)
Net assets acquired and liabilities assumed	$ 114,553

Earnings per Share (Narrative)

Earnings per Share (Narrative) (Details) - $ / shares	3 Months Ended												12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Earnings Per Share [Abstract]
Dividend Declared And Paid	$ 0.32	$ 0.32	$ 0.32	$ 0.32	$ 0.27	$ 0.27	$ 0.27	$ 0.27	$ 0.25	$ 0.25	$ 0.25	$ 0.25
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount													213,248	288,133	293,898
Exercised, Number of Shares													223,405	338,748	420,524

(Schedule of Earnings Per Share

(Schedule of Earnings Per Share, Basic and Diluted) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Components of Earnings Per Share, Basic and Diluted [Line Items]
Distributed earnings									$ 51,621	$ 43,207	$ 39,627
Undistributed earnings									68,909	70,683	42,470
Net income	$ 32,164	$ 29,739	$ 29,948	$ 28,679	$ 40,621	$ 27,937	$ 24,214	$ 21,118	120,530	113,890	82,097
Common Stock, Class A
Components of Earnings Per Share, Basic and Diluted [Line Items]
Basic net income available to common stockholders									$ 81,087	$ 76,294	$ 54,715
Basic weighted average common shares outstanding	27,207	27,139	27,082	26,992	26,933	26,822	26,707	26,584	27,105	26,763	26,354
Basic earnings per share	$ 0.80	$ 0.74	$ 0.74	$ 0.71	$ 1.01	$ 0.70	$ 0.61	$ 0.53	$ 2.99	$ 2.85	$ 2.08
Diluted net income available to common stockholders									$ 81,405	$ 76,555	$ 54,937
Effect of potential exercise of stock options									328	279	324
Diluted weighted average common shares outstanding	27,528	27,413	27,409	27,367	27,279	27,128	26,936	26,819	27,433	27,042	26,678
Diluted earnings per share	$ 0.79	$ 0.73	$ 0.74	$ 0.71	$ 1	$ 0.69	$ 0.60	$ 0.53	$ 2.97	$ 2.83	$ 2.06
Common Stock, Class B
Components of Earnings Per Share, Basic and Diluted [Line Items]
Basic net income available to common stockholders									$ 39,443	$ 37,596	$ 27,382
Basic weighted average common shares outstanding	13,177	13,187	13,187	13,187	13,188	13,188	13,188	13,188	13,185	13,188	13,189
Basic earnings per share	$ 0.80	$ 0.74	$ 0.74	$ 0.71	$ 1.01	$ 0.70	$ 0.61	$ 0.53	$ 2.99	$ 2.85	$ 2.08
Diluted net income available to common stockholders									$ 39,125	$ 37,335	$ 27,160
Diluted weighted average common shares outstanding	13,177	13,187	13,187	13,187	13,188	13,188	13,188	13,188	13,185	13,188	13,189
Diluted earnings per share	$ 0.79	$ 0.73	$ 0.74	$ 0.71	$ 1	$ 0.69	$ 0.60	$ 0.53	$ 2.97	$ 2.83	$ 2.06

Property and Equipment (Propert

Property and Equipment (Property and Equipment) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Abstract]
Furniture and equipment	$ 194,470	$ 150,640
Leasehold improvements	62,293	49,625
Finance leases	705	641
Property and equipment-gross	257,468	200,906
Accumulated depreciation and amortization	(136,172)	(115,275)
Property and equipment-net	$ 121,296	$ 85,631

Property and Equipment (Narrati

Property and Equipment (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Abstract]
Depreciation and Amortization Expense	$ 39.5	$ 27.6	$ 25.5

Goodwill and Other Intangible_3

Goodwill and Other Intangible Assets (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Amortization of Intangible Assets	$ 27.6	$ 25.4	$ 26.3
Capitalized software
Finite-Lived Intangible Assets [Line Items]
Impairment of Intangible Assets, Finite-lived	$ 1.4

Goodwill and Other Intangible_4

Goodwill and Other Intangible Assets (Schedule of Goodwill) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Goodwill [Roll Forward]
Goodwill balance, period start	$ 1,191,259	$ 1,085,806
Acquisitions	46,624	105,453
Acquisition fair value adjustment	11
Goodwill balance, period end	$ 1,237,894	$ 1,191,259

Goodwill and Other Intangible_5

Goodwill and Other Intangible Assets (Schedule of Other Intangible Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 485,237	$ 454,943
Accumulated Amortization	283,006	258,165
Net Carrying Amount	202,231	196,778
Contract and program intangible assets
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	430,632	402,532
Accumulated Amortization	242,194	221,437
Net Carrying Amount	188,438	181,095
Capitalized software
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	54,605	52,411
Accumulated Amortization	40,812	36,728
Net Carrying Amount	$ 13,793	$ 15,683

Goodwill and Other Intangible_6

Goodwill and Other Intangible Assets (Schedule of Other Intangible Assets, Future Amortization Expense) (Details) $ in Thousands	Dec. 31, 2020USD ($)
Year ending:
December 31, 2021	$ 24,581
December 31, 2022	24,232
December 31, 2023	19,612
December 31, 2024	17,486
December 31, 2025	$ 15,423

Debt (Revolving Credit Facility

Debt (Revolving Credit Facility) (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Debt, Weighted Average Interest Rate	2.32%	4.11%
Bank of America Syndicate [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 500,000,000
Long-term Line of Credit	15,000,000	$ 36,500,000
Line of Credit Facility, Weighted Average Borrowings	37,300,000	37,000,000
Line of Credit Facility, Maximum Available Borrowing	478,800,000
Bank of America Syndicate [Member] | Letter of Credit [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	75,000,000
Letters of Credit Outstanding, Amount	6,200,000	$ 5,800,000
Bank of America Syndicate [Member] | Revolving Credit Facility, Swing Line Loan [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 30,000,000
London Interbank Offered Rate (LIBOR) [Member] | Revolving Credit Facility [Member] | Minimum [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.25%
London Interbank Offered Rate (LIBOR) [Member] | Revolving Credit Facility [Member] | Maximum [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate	2.25%
Bank of America's Base Rate [Member] | Revolving Credit Facility [Member] | Minimum [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate	0.25%
Bank of America's Base Rate [Member] | Revolving Credit Facility [Member] | Maximum [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.25%

Commitments and Contingencies_2

Commitments and Contingencies (Letter of Credit) (Narrative) (Details) - Bank of America Syndicate [Member] - Letter of Credit [Member] - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Line of Credit Facility [Line Items]
Letters of Credit Outstanding, Amount	$ 6.2	$ 5.8
Performance Guarantee [Member]
Line of Credit Facility [Line Items]
Letters of Credit Outstanding, Amount	$ 5.7

Stockholders Equity and Stock_3

Stockholders Equity and Stock-Based Compensation (Narrative) (Details) - USD ($)	Jan. 02, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Stockholders Equity and Stock-Based Compensation [Line Items]
Treasury Stock, Shares		244,113	244,113
Class B Share Convertible to Class A Share		one
Preferred Stock, Shares Authorized		20,000,000
Preferred Stock, Par Value Per Share		$ 0.01
Preferred Stock, Shares Outstanding		0	0
Stock-based Compensation Arrangement by Stock-based Payment Award, Number of Shares Authorized		15,751,005
Stock-based Compensation Arrangement by Stock-based Payment Award, Number of Shares Available for Issuance		7,160,951
Stock-based Compensation Expense		$ 11,400,000	$ 7,500,000	$ 5,100,000
Employee Services Stock-based Compensation Expense, Capitalized Amount		0	0	0
Share-based Payment Arrangement, Expense, Tax Benefit		$ (1,600,000)	$ (2,100,000)	$ (3,400,000)
Stock-based Compensation Arrangement by Stock-based Award, Award Vesting Period			3 years	3 years
Stock-based Compensation Arrangement by Stock-based Payment Award, Expiration Period			5 years	5 years
Granted, Number of Shares		0	489,947	466,828
Expected Annual Cash Dividend			$ 1.08	$ 1
Granted, Weighted Average Fair Value			$ 12.07	$ 10.42
Stock-based Payment Award, Options, Vested, Fair Value		$ 3,600,000	$ 2,500,000	$ 1,500,000
Employee Service Stock-based Compensation, Nonvested Awards, Compensation Cost Not Yet Recognized		$ 3,000,000
Stock-based Compensation, Nonvested Awards, Total Compensation Cost Not Yet Recognized, Period for Recognition		1 year
Performance-based restricted stock units [Member]
Stockholders Equity and Stock-Based Compensation [Line Items]
Stock-based Compensation Arrangement by Stock-based Award, Award Vesting Period		2 years	2 years
Common Stock, Class A
Stockholders Equity and Stock-Based Compensation [Line Items]
Common Stock, Shares Authorized		150,000,000	150,000,000
Common Stock, Par Value Per Share		$ 0.01	$ 0.01
Common Stock, Shares Outstanding		27,294,361	26,991,747
Common Stock, Voting Rights		one
Common Stock, Class B
Stockholders Equity and Stock-Based Compensation [Line Items]
Common Stock, Shares Authorized		50,000,000	50,000,000
Common Stock, Par Value Per Share		$ 0.01	$ 0.01
Common Stock, Shares Outstanding		13,176,695	13,187,195
Common Stock, Voting Rights		ten
Maximum [Member]
Stockholders Equity and Stock-Based Compensation [Line Items]
Stock-based Compensation Arrangement by Stock-based Payment Award, Expiration Period			8 years	8 years
Going Private Transaction [Member] | Common Stock, Class A
Stockholders Equity and Stock-Based Compensation [Line Items]
Common Stock, Voting Rights		one
Going Private Transaction [Member] | Common Stock, Class B
Stockholders Equity and Stock-Based Compensation [Line Items]
Common Stock, Voting Rights		one
Subsequent Event [Member]
Stockholders Equity and Stock-Based Compensation [Line Items]
Annual Percentage Increase In Number Of Shares Available For Issuance	1.50%
Stock-based Compensation Arrangement by Stock-based Payment Award, Number of Additional Shares Authorized	607,066
Director [Member] | Restricted Stock [Member]
Stockholders Equity and Stock-Based Compensation [Line Items]
Stock-based Compensation Arrangement by Stock-based Award, Award Vesting Period		1 year	1 year

Stockholders Equity and Stock_4

Stockholders Equity and Stock-Based Compensation (Schedule of Shared-based Payment Award, Stock Options, Valuation Assumptions) (Detail)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Stockholders Equity and Stock-Based Compensation [Abstract]
Volatility	27.21%	26.57%
Expected life of options	3 years	3 years
Risk-free interest rate	1.98%	2.72%
Dividend yield	1.76%	2.00%

Stockholders Equity and Stock_5

Stockholders Equity and Stock-Based Compensation (Schedule of Share-based Compensation, Stock Options, Activity) (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Payment Award, Options, Outstanding [Roll Forward]
Stock options, Number of Shares, Period Start	1,136,095	1,093,400	1,169,408
Granted, Number of Shares	0	489,947	466,828
Exercised, Number of Shares	(223,405)	(338,748)	(420,524)
Cancelled and expired, Number of Shares	(126,863)	(108,504)	(122,312)
Stock options, Number of Shares, Period End	785,827	1,136,095	1,093,400
Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Stock options, Weighted Average Exercise Price, Period Start	$ 54.98	$ 45.34	$ 35.88
Granted, Weighted Average Exercise Price		63.87	54.87
Exercised, Weighted Average Exercise Price	46.72	37.94	30.05
Cancelled and expired, Weighted Average Exercise Price	61.17	51.21	43.85
Stock options, Weighted Average Exercise Price, Period End	$ 56.33	$ 54.98	$ 45.34
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Stock options, Aggregate Intrinsic Value	$ 25,629	$ 28,291	$ 8,776	$ 16,731
Exercised, Aggregate Intrinsic Value	$ 6,897	$ 9,641	$ 12,411
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Remaining Contractual Term	3 years
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable, Number	432,184
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable, Weighted Average Exercise Price	$ 52.05
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable, Aggregate Intrinsic Value	$ 15,944
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable, Weighted Average Remaining Contractual Term	2 years

Stockholders Equity and Stock_6

Stockholders Equity and Stock-Based Compensation (Schedule of Non-Vested Share Activity) (Detail)	12 Months Ended
	Dec. 31, 2020$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested [Roll Forward]
Non-vested stock options, Number of Shares, Period Start | shares	845,555
Vested, Number of Shares | shares	(368,592)
Cancelled, Number of Shares | shares	(123,320)
Non-vested stock options, Number of Shares, Period End | shares	353,643
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]
Non-vested stock options, Weighted Average Fair Value, Period Start | $ / shares	$ 10.88
Vested, Weighted Average Fair Value | $ / shares	9.88
Cancelled, Weighted Average Fair Value | $ / shares	11.63
Non-vested stock options, Weighted Average Fair Value, Period End | $ / shares	$ 11.66

Stockholders Equity and Stock_7

Stockholders Equity and Stock-Based Compensation (Schedule of Share-based Compensation, Restricted Stock Activity) (Details) - Restricted Stock [Member] - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award, Restricted Stock, Non-vested
Non-vested, Period Start	24,000	20,000
Granted	24,000	24,000
Vested	(24,000)	(20,000)
Non-vested, Period End	24,000	24,000
Share-based Compensation Arrangement by Share-based Payment Award, Restricted Stock, Weighted Average Fair Value
Non-vested, Weighted Average Fair Value, Period Start	$ 62.66	$ 52.83
Granted, Weighted Average Fair Value	71.11	62.66
Vested, Weighted Average Fair Value	62.66	52.83
Non-vested, Weighted Average Fair Value, Period End	$ 71.11	$ 62.66

Stockholders Equity and Stock_8

Stockholders Equity and Stock-Based Compensation Schedule of Share-based Compensation, Restricted Stock Unit Activity (Details) - Restricted Stock Units (RSUs) [Member] - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award, Restricted Stock Units, Number of Shares [Roll Forward]
Non-vested, Period Start	210,827	137,596
Granted	266,880	145,440
Vested	(73,047)	(60,915)
Forfeited	(57,861)	(11,294)
Non-vested, Period End	346,799	210,827
Share-based Compensation Arrangement by Share-based Payment Award, Restricted Stock Units, Weighted Average Fair Value
Non-vested, Weighted Average Fair Value, Period Start	$ 55.31	$ 45.11
Granted, Weighted Average Fair Value	68.83	59.43
Vested, Weighted Average Fair Value	53.85	42.75
Forfeited, Weighted Average Fair Value	64.52	51.88
Non-vested, Weighted Average Fair Value, Period End	$ 64.48	$ 55.31

Retirement Plans (Narrative) (D

Retirement Plans (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Retirement Plan [Line Items]
Defined Contribution Plan, Other Than Employee Stock Ownership Plan, Contributions	$ 33	$ 26.7	$ 23.5
Employee Supplemental Savings Plan (ESSP) Percentage of Annual Base Compensation		75.00%	75.00%
Employee Supplemental Savings Plan (ESSP) Percentage of Bonus		100.00%	100.00%
Employee Supplemental Savings Plan (ESSP), Employee Contribution	$ 0.5	$ 3.4	$ 3.4
Defined Benefit Plan, Plan Assets, Actual Allocation, Percentage	100.00%	100.00%
Defined Benefit Plan, Benefit Obligation	$ 0.7	$ 0.7

Income Taxes (Narrative) (Detai

Income Taxes (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Contingency [Line Items]
Income Taxes Paid, Net of Refunds	$ 23.9	$ 21.4
Income Taxes Refund, Net of Payments			$ (4.3)
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	11.7	9.6	$ 0.4
Unrecognized Tax Benefits, Period Increase (Decrease)	2.1
Unrecognized Tax Benefits, Increase Resulting from Research and Development Credits in Current Year Years	1.8	1.8
Unrecognized Tax Benefits, Increase Resulting from Research and Development Credits in Prior Years		$ 7.7
State [Member]
Income Tax Contingency [Line Items]
Operating Loss Carryforwards	9.5
Foreign Tax Authority [Member]
Income Tax Contingency [Line Items]
Operating Loss Carryforwards	$ 1.7

Income Taxes (Schedule of Incom

Income Taxes (Schedule of Income before Income Tax, Domestic and Foreign) (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Domestic									$ 156,496	$ 136,164	$ 110,514
Foreign									(99)	(66)	91
INCOME FROM OPERATIONS BEFORE INCOME TAXES AND EQUITY METHOD INVESTMENTS	$ 39,993	$ 39,042	$ 39,091	$ 38,271	$ 37,604	$ 37,794	$ 32,504	$ 28,196	$ 156,397	$ 136,098	$ 110,605

Income Taxes (Schedule of Compo

Income Taxes (Schedule of Components of Income Tax Expense) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Federal	$ 16,296,000	$ (9,092,000)	$ 11,602,000
State	7,463,000	6,015,000	4,937,000
Foreign	140,000	97,000	133,000
Current provision (benefit)	23,899,000	(2,980,000)	16,672,000
Federal	8,183,000	13,451,000	8,010,000
State	1,710,000	2,301,000	3,586,000
Deferred provision	9,893,000	15,752,000	11,596,000
Federal	1,996,000	9,440,000	234,000
State	87,000	0	28,000
Foreign	(10,000)	0	0
Non-current provision resulting from allocating tax benefits directly to changes in liabilities	2,073,000	9,440,000	262,000
Provision for income taxes	$ 35,865,000	$ 22,212,000	$ 28,530,000

Income Taxes (Schedule of Effec

Income Taxes (Schedule of Effective Income Tax Rate Reconciliation) (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Statutory U.S. Federal tax rate	21.00%	21.00%	21.00%
Increase (decrease) in tax rate resulting from:
State taxes—net of Federal benefit	4.90%	4.80%	6.10%
Research and development credit	(1.80%)	(8.80%)	0.00%
Stock-based compensation	(0.90%)	(1.30%)	(2.20%)
ESSP	(0.70%)	(1.00%)	0.40%
Excess executive compensation	0.70%	0.80%	0.80%
Other, net	(0.30%)	0.80%	(0.30%)
Effective tax rate	22.90%	16.30%	25.80%

Income Taxes (Schedule of Defer

Income Taxes (Schedule of Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Goodwill and other intangibles	$ 152,412	$ 136,882
Lease arrangements	25,863	31,128
Property and equipment	17,237	13,270
Unbilled receivables - IRC Section 481(a)	2,946	5,878
Gross deferred tax liabilities	198,458	187,158
Lease obligations	(28,652)	(34,146)
Retirement and other liabilities	(23,071)	(18,614)
Allowance for potential contract losses and other contract reserves	(4,815)	(2,205)
Foreign and state operating loss carryforwards	(2,253)	(2,239)
Less: Valuation allowance	1,971	1,828
Gross deferred tax assets	(56,820)	(55,376)
Net deferred tax liabilities	$ 141,638	$ 131,782

Income Taxes (Schedule of Unrec

Income Taxes (Schedule of Unrecognized Tax Benefits Roll Forward) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reconciliation of Unrecognized Tax Benefits [Roll Forward]
Gross unrecognized tax benefits at beginning of year	$ 9,635,000	$ 490,000	$ 220,000
Increases in tax positions for current year	1,712,000	1,839,000	320,000
Increases in tax positions for prior years	371,000	7,718,000	36,000
Lapse in statute of limitations	(10,000)	0	(86,000)
Decreases in tax positions for prior years	0	(412,000)	0
Gross unrecognized tax benefits at end of year	$ 11,708,000	$ 9,635,000	$ 490,000

Quarterly Financial Informati_3

Quarterly Financial Information (Unaudited) (Schedule of Quarterly Financial Information) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Quarterly Financial Information Disclosure [Line Items]
Revenues	$ 638,784	$ 636,196	$ 632,492	$ 610,912	$ 604,413	$ 579,179	$ 537,037	$ 501,930	$ 2,518,384	$ 2,222,559	$ 1,958,557
Operating income	40,224	39,341	39,586	38,898	38,094	38,402	33,297	28,532	158,049	138,325	112,742
Income from operations before income taxes and equity method investments	39,993	39,042	39,091	38,271	37,604	37,794	32,504	28,196	156,397	136,098	110,605
Net income	$ 32,164	$ 29,739	$ 29,948	$ 28,679	$ 40,621	$ 27,937	$ 24,214	$ 21,118	$ 120,530	$ 113,890	$ 82,097
Common Stock, Class A
Quarterly Financial Information Disclosure [Line Items]
Basic weighted average common shares outstanding	27,207	27,139	27,082	26,992	26,933	26,822	26,707	26,584	27,105	26,763	26,354
Basic earnings per share	$ 0.80	$ 0.74	$ 0.74	$ 0.71	$ 1.01	$ 0.70	$ 0.61	$ 0.53	$ 2.99	$ 2.85	$ 2.08
Diluted weighted average common shares outstanding	27,528	27,413	27,409	27,367	27,279	27,128	26,936	26,819	27,433	27,042	26,678
Diluted earnings per share	$ 0.79	$ 0.73	$ 0.74	$ 0.71	$ 1	$ 0.69	$ 0.60	$ 0.53	$ 2.97	$ 2.83	$ 2.06
Common Stock, Class B
Quarterly Financial Information Disclosure [Line Items]
Basic weighted average common shares outstanding	13,177	13,187	13,187	13,187	13,188	13,188	13,188	13,188	13,185	13,188	13,189
Basic earnings per share	$ 0.80	$ 0.74	$ 0.74	$ 0.71	$ 1.01	$ 0.70	$ 0.61	$ 0.53	$ 2.99	$ 2.85	$ 2.08
Diluted weighted average common shares outstanding	13,177	13,187	13,187	13,187	13,188	13,188	13,188	13,188	13,185	13,188	13,189
Diluted earnings per share	$ 0.79	$ 0.73	$ 0.74	$ 0.71	$ 1	$ 0.69	$ 0.60	$ 0.53	$ 2.97	$ 2.83	$ 2.06

Schedule II (Valuation and Qual

Schedule II (Valuation and Qualifying Accounts) (Details) - USD ($)		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Doubtful Accounts
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period		$ 11,578,000	$ 6,233,000	$ 6,157,000
Charged to Costs and Expenses		5,244,000	3,000,000	0
Deductions		0	0	0
Other*	[1]	1,555,000	2,345,000	76,000
Balance at End of Period		18,377,000	11,578,000	6,233,000
Deferred Tax Asset Valuation
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period		1,828,000	1,537,000	717,000
Charged to Costs and Expenses		143,000	291,000	820,000
Deductions		0	0	0
Other		0	0	0
Balance at End of Period		$ 1,971,000	$ 1,828,000	$ 1,537,000
[1]	Other represents doubtful account reserves released or recorded as part of net revenues for estimated customer disallowances.