CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (UNAUDITED) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Income Statement [Abstract]
Service revenues	$ 1,475,937	$ 1,716,335
Costs of services	913,140	1,026,603
Gross margin	562,797	689,732
Selling, general and administrative expenses	521,595	552,229
Income from investments held in employee deferred compensation trusts (which is completely offset by related costs and expenses - Note A)	(43,376)	(27,291)
Amortization of intangible assets	304	721
Interest income, net	(6,413)	(4,825)
Income before income taxes	90,687	168,898
Provision for income taxes	26,986	46,893
Net income	$ 63,701	$ 122,005
Net income per share:
Basic (in usd per share)	$ 0.61	$ 1.15
Diluted (in usd per share)	$ 0.61	$ 1.14
Weighted average shares:
Basic (in shares)	103,787	106,420
Diluted (in shares)	104,399	107,130
Dividends declared per share (in usd per share)	$ 0.53	$ 0.48