Revenue - Contract Assets and Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Aug. 02, 2021	Dec. 31, 2020
Disaggregation of Revenue [Line Items]
Unbilled service fees	$ 116,558		$ 30,570
Unbilled outside vendor costs, billable to clients	63,065		11,063
Advance billings	361,885		$ 66,418
Increase in contract liability balance	295,467
Revenue recognized	64,446
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation, amount	$ 22,812
MDC
Disaggregation of Revenue [Line Items]
Advance billings		$ (211,403)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Expected timing of satisfaction	1 year
Remaining performance obligation	93.00%
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Expected timing of satisfaction
Remaining performance obligation	7.00%
Accrued Expenses and Other Current Liabilities
Disaggregation of Revenue [Line Items]
Increase in contract assets	$ 99,853