CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (UNAUDITED) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Income Statement [Abstract]
Service revenues	$ 1,472,524	$ 1,639,478	$ 2,948,461	$ 3,355,813
Costs of services	895,845	979,309	1,808,985	2,005,912
Gross margin	576,679	660,169	1,139,476	1,349,901
Selling, general and administrative expenses	500,832	541,904	1,022,427	1,094,133
Income from investments held in employee deferred compensation trusts (which is completely offset by related costs and expenses - Note A)	(15,733)	(28,347)	(59,109)	(55,638)
Amortization of intangible assets	304	721	608	1,442
Interest income, net	(5,186)	(5,320)	(11,599)	(10,145)
Income before income taxes	96,462	151,211	187,149	320,109
Provision for income taxes	28,306	44,919	55,292	91,812
Net income	$ 68,156	$ 106,292	$ 131,857	$ 228,297
Net income per share:
Basic (in usd per share)	$ 0.66	$ 1.00	$ 1.27	$ 2.15
Diluted (in usd per share)	$ 0.66	$ 1.00	$ 1.27	$ 2.14
Weighted average shares:
Basic (in shares)	103,151	106,102	103,469	106,260
Diluted (in shares)	103,328	106,422	103,864	106,775
Dividends declared per share (in usd per share)	$ 0.53	$ 0.48	$ 1.06	$ 0.96