Business Segments - Reconciliation of Revenue and Operating Income by Reportable Segment to Consolidated Results (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Segment Reporting Information [Line Items]
Service revenues	$ 6,392,517	$ 7,238,142	$ 6,461,444
Segment income	555,493	890,614	805,824
Amortization of intangible assets	2,883	1,667	2,241
Interest income, net	(23,973)	(8,008)	(197)
Income before income taxes	576,583	896,955	803,780
Contract talent solutions
Segment Reporting Information [Line Items]
Service revenues	3,895,332	4,532,847	4,038,743
Segment income	292,815	492,281	393,872
Permanent placement talent solutions
Segment Reporting Information [Line Items]
Service revenues	567,486	725,155	569,921
Segment income	75,004	127,622	106,465
Protiviti
Segment Reporting Information [Line Items]
Service revenues	1,929,699	1,980,140	1,852,780
Segment income	$ 187,674	$ 270,711	$ 305,487