Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 211,860	$ 341,591
Adjustments to reconcile net income to net cash provided by operating activities:
Allowance for credit losses	4,579	6,501
Depreciation	47,097	48,485
Amortization of cloud computing implementation costs	12,631	1,660
Amortization of intangible assets	1,002	1,022
Realized and unrealized gain from investments held in employee deferred compensation trusts	(32,743)	(31,034)
Stock-based compensation	39,623	34,803
Deferred income taxes	(20,021)	(9,685)
Changes in operating assets and liabilities:
Accounts receivable	138,350	(72,288)
Capitalized cloud computing implementation costs	(26,121)	(20,872)
Accounts payable and accrued expenses	9,030	(7,537)
Accrued payroll and benefit cost	152,007	138,200
Income taxes payable	15,284	(6,734)
Other assets and liabilities, net	12,063	14,894
Net cash flows provided by operating activities	564,641	439,006
CASH FLOWS FROM INVESTING ACTIVITIES:
Capital expenditures	(28,878)	(45,138)
Investments in employee deferred compensation trusts	(48,205)	(52,367)
Proceeds from employee deferred compensation trust redemptions	33,651	23,976
Net cash flows used in investing activities	(43,432)	(73,529)
CASH FLOWS FROM FINANCING ACTIVITIES:
Repayment of notes payable	(162)	(148)
Repurchases of common stock	(91,013)	(214,047)
Dividends paid	(117,301)	(109,702)
Net cash flows used in financing activities	(208,476)	(323,897)
Effect of exchange rate fluctuations	3,789	(5,418)
Change in cash and cash equivalents	316,522	36,162
Cash and cash equivalents at beginning of period	270,478	276,579
Cash and cash equivalents at end of period	587,000	312,741
Non-cash items:
Stock repurchases awaiting settlement	2,640	5,482
Fund exchanges within employee deferred compensation trusts	$ 182,616	$ 30,054