CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Income Statement [Abstract]
Service revenues	$ 5,795,837	$ 6,392,517	$ 7,238,142
Costs of services	3,548,607	3,817,513	4,144,093
Gross margin	2,247,230	2,575,004	3,094,049
Selling, general and administrative expenses	2,004,539	2,107,531	2,117,296
(Income) loss from investments held in employee deferred compensation trusts (which is completely offset by related costs and expenses - Note A)	(94,079)	(88,020)	86,139
Amortization of intangible assets	1,217	2,883	1,667
Interest income, net	(22,118)	(23,973)	(8,008)
Income before income taxes	357,671	576,583	896,955
Provision for income taxes	106,073	165,437	239,036
Net income	$ 251,598	$ 411,146	$ 657,919
Net income per share:
Basic (usd per share)	$ 2.45	$ 3.90	$ 6.08
Diluted (usd per share)	$ 2.44	$ 3.88	$ 6.03
Weighted average shares:
Basic (in shares)	102,661	105,530	108,214
Diluted (in shares)	103,028	106,074	109,171
Dividends declared per share (in usd per share)	$ 2.12	$ 1.92	$ 1.72