Summary of Significant Accounting Policies - Additional Information (Details)		12 Months Ended
	Dec. 31, 2021 USD ($)	Dec. 31, 2021 USD ($) Segment	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Contract payment term description		contracts typically contain billing terms that provide for invoicing monthly or upon completion of milestones,  and payment on a net 30-day basis.
Contracts payment, term		30 days
Number of reportable segments | Segment		1
Goodwill, impaired, accumulated impairment loss	$ 0	$ 0
Goodwill, impairment loss		$ 0
Performance based share awards, performance period		3 years
Number of operating segments | Segment		1
Revenue		$ 1,553,048,000	$ 1,506,875,000	$ 1,478,525,000
Foreign financial institutions, actual deposits	20,100,000	20,100,000	81,500,000
Domestic bank accounts exceeded FDIC insurance limit	2,000,000.0	2,000,000.0
Federal Government Agencies And Departments
Summary Of Significant Accounting Policies [Line Items]
Revenue		$ 735,000,000.0	$ 667,000,000.0	$ 561,000,000.0
Federal Government Agencies And Departments | Customer Concentration Risk | Sales Revenue, Net
Summary Of Significant Accounting Policies [Line Items]
Concentration risk, percentage		47.00%	44.00%	38.00%
International Clients | Geographic Concentration Risk | Sales Revenue, Net
Summary Of Significant Accounting Policies [Line Items]
Concentration risk, percentage		11.00%	13.00%	8.00%
International | Geographic Concentration Risk | Long-Lived Assets
Summary Of Significant Accounting Policies [Line Items]
Concentration risk, percentage		15.00%	15.00%
Other Assets
Summary Of Significant Accounting Policies [Line Items]
Capitalized software, net of accumulated amortization	$ 14,500,000	$ 14,500,000	$ 4,800,000
Indirect and Selling Expenses
Summary Of Significant Accounting Policies [Line Items]
Impairment expense related to intangible assets		$ 7,900,000	$ 3,100,000	$ 1,700,000
Minimum
Summary Of Significant Accounting Policies [Line Items]
Property and equipment, estimated useful life		2 years
Finite-lived intangible asset, useful life	1 year
Minimum | Other Assets
Summary Of Significant Accounting Policies [Line Items]
Finite-lived intangible asset, useful life		3 years
Maximum
Summary Of Significant Accounting Policies [Line Items]
Property and equipment, estimated useful life		7 years
Finite-lived intangible asset, useful life	10 years
Insured domestic bank accounts	$ 250,000	$ 250,000
Maximum | Other Assets
Summary Of Significant Accounting Policies [Line Items]
Finite-lived intangible asset, useful life		5 years