Condensed Consolidated Statements of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Income Statement [Abstract]
Service revenues	$ 1,814,834	$ 1,398,380
Costs of services	1,042,988	836,669
Gross margin	771,846	561,711
Selling, general and administrative expenses	514,194	423,062
(Income) loss from investments held in employee deferred compensation trusts (which is completely offset by related costs and expenses - Notes A & I)	30,001	(11,988)
Amortization of intangible assets	417	576
Interest income, net	(166)	(45)
Income before income taxes	227,400	150,106
Provision for income taxes	59,161	39,508
Net income	$ 168,239	$ 110,598
Net income per share:
Basic (in usd per share)	$ 1.54	$ 0.99
Diluted (in usd per share)	$ 1.52	$ 0.98
Shares:
Basic (in shares)	109,218	111,424
Diluted (in shares)	110,591	112,496
Dividends declared per share (in usd per share)	$ 0.43	$ 0.38