CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
REVENUES
Customer services	$ 2,695,823	$ 2,424,300	$ 2,161,220
COSTS AND EXPENSES
Cost of services provided (exclusive of depreciation and amortization below)	1,308,399	1,162,617	1,048,592
Sales, general and administrative	802,710	727,489	657,209
Depreciation and amortization	91,326	86,558	79,331
Total operating expenses	2,202,435	1,976,664	1,785,132
OPERATING INCOME	493,388	447,636	376,088
Interest expense, net	2,638	830	5,082
Other (income) expense, net	(8,167)	(35,679)	8,290
CONSOLIDATED INCOME BEFORE INCOME TAXES	498,917	482,485	362,716
PROVISION FOR INCOME TAXES	130,318	125,920	95,960
NET INCOME	$ 368,599	$ 356,565	$ 266,756
NET INCOME PER SHARE - BASIC	$ 0.75	$ 0.72	$ 0.54
NET INCOME PER SHARE - DILUTED	$ 0.75	$ 0.72	$ 0.54
Weighted average shares outstanding - basic	492,300	492,054	491,604
Weighted average shares outstanding - diluted	492,413	492,054	491,604
DIVIDENDS PAID PER SHARE	$ 0.43	$ 0.42	$ 0.33