Business Combinations and Acquisitions - Schedule of Recognized Identified Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Nov. 23, 2020	Nov. 20, 2020	Dec. 31, 2019	Dec. 31, 2018
Business Acquisition [Line Items]
Goodwill	$ 590,668			$ 409,588	$ 408,025
CENTRA
Business Acquisition [Line Items]
Cash and cash equivalents			$ 3,202
Accounts receivable			72,636
Prepaid expenses and other current assets			3,454
Property and equipment			2,848
Operating lease right-of-use assets			21,137
Intangible assets			74,100
Total assets acquired			177,377
Accounts payable			30,212
Accrued expenses			1,159
Customer advances and billings in excess of costs			2,965
Salaries, benefits and payroll taxes			7,969
Deferred income taxes			12,402
Operating lease liabilities, current portion			2,996
Other current liabilities			1,423
Long-term operating lease liabilities			18,038
Total liabilities assumed			77,164
Net identifiable assets acquired			100,213
Goodwill			125,113
Total estimated consideration transferred			$ 225,326
Metis Solution
Business Acquisition [Line Items]
Cash and cash equivalents		$ 5,469
Accounts receivable		15,905
Prepaid expenses and other current assets		621
Property and equipment		27
Operating lease right-of-use assets		599
Intangible assets		37,800
Other noncurrent assets		63
Total assets acquired		60,484
Accounts payable		2,454
Accrued expenses		1,056
Customer advances and billings in excess of costs		3,420
Salaries, benefits and payroll taxes		5,486
Deferred income taxes		7,700
Operating lease liabilities, current portion		355
Long-term operating lease liabilities		240
Total liabilities assumed		20,711
Net identifiable assets acquired		39,773
Goodwill		55,967
Total estimated consideration transferred		$ 95,740