Business Segments - Reconciliation of Revenue and Operating Income by Reportable Segment to Consolidated Results (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Segment Reporting Information [Line Items]
Service revenues	$ 7,238,142	$ 6,461,444	$ 5,109,000
Segment income	890,614	805,824	421,758
Amortization of intangible assets	1,667	2,241	1,219
Interest income, net	(8,008)	(197)	(1,343)
Income before income taxes	896,955	803,780	421,882
Contract talent solutions
Segment Reporting Information [Line Items]
Service revenues	4,532,847	4,038,743	3,477,335
Segment income	492,281	393,872	237,279
Permanent placement talent solutions
Segment Reporting Information [Line Items]
Service revenues	725,155	569,921	370,109
Segment income	127,622	106,465	28,799
Protiviti
Segment Reporting Information [Line Items]
Service revenues	1,980,140	1,852,780	1,261,556
Segment income	$ 270,711	$ 305,487	$ 155,680