Revenue Recognition - Schedule of Revenue Disaggregated by Line of Business (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2022 USD ($) segment	Sep. 30, 2021 USD ($)
Revenue from Contract with Customer [Abstract]
Number of reportable segments \| segment			3
Guarantee period			90 days
Disaggregation of Revenue [Line Items]
Service revenues	$ 1,833,455	$ 1,712,566	$ 5,511,116	$ 4,691,527
Elimination of intersegment revenues
Disaggregation of Revenue [Line Items]
Service revenues	(132,745)	(172,534)	(414,493)	(419,375)
Finance and accounting
Disaggregation of Revenue [Line Items]
Service revenues	805,229	732,365	2,417,829	1,996,692
Administrative and customer support
Disaggregation of Revenue [Line Items]
Service revenues	250,531	279,370	809,578	763,035
Technology
Disaggregation of Revenue [Line Items]
Service revenues	216,735	215,500	648,252	581,905
Total contract talent solutions
Disaggregation of Revenue [Line Items]
Service revenues	1,139,750	1,054,701	3,461,166	2,922,257
Permanent placement talent solutions
Disaggregation of Revenue [Line Items]
Service revenues	182,329	156,444	569,207	411,788
Protiviti
Disaggregation of Revenue [Line Items]
Service revenues	$ 511,376	$ 501,421	$ 1,480,743	$ 1,357,482