Revenue Recognition - Schedule of Revenue Disaggregated by Line of Business (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2022 USD ($) segment	Jun. 30, 2021 USD ($)
Revenue from Contract with Customer [Abstract]
Number of reportable segments | segment			3
Guarantee period			90 days
Disaggregation of Revenue [Line Items]
Service revenues	$ 1,862,827	$ 1,580,581	$ 3,677,661	$ 2,978,961
Elimination of intersegment revenues
Disaggregation of Revenue [Line Items]
Service revenues	(137,548)	(143,036)	(281,748)	(246,840)
Finance and accounting
Disaggregation of Revenue [Line Items]
Service revenues	810,910	663,892	1,612,600	1,264,326
Administrative and customer support
Disaggregation of Revenue [Line Items]
Service revenues	274,141	263,192	559,047	483,665
Technology
Disaggregation of Revenue [Line Items]
Service revenues	218,190	194,233	431,517	366,406
Total contract talent solutions
Disaggregation of Revenue [Line Items]
Service revenues	1,165,693	978,281	2,321,416	1,867,557
Permanent placement talent solutions
Disaggregation of Revenue [Line Items]
Service revenues	200,096	143,640	386,878	255,344
Protiviti
Disaggregation of Revenue [Line Items]
Service revenues	$ 497,038	$ 458,660	$ 969,367	$ 856,060