Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 259,811	$ 136,111
Adjustments to reconcile net income to net cash provided by operating activities:
Allowance for credit losses	4,733	6,713
Depreciation	27,715	31,509
Amortization of cloud computing implementation costs	13,353	7,569
Amortization of intangible assets	1,152	668
Realized and unrealized (gains) losses from investments held in employee deferred compensation trusts	(36,949)	(7,091)
Stock-based compensation	28,085	26,560
Deferred income taxes	(5,524)	(4,289)
Changes in operating assets and liabilities:
Accounts receivable	(201,602)	153,913
Capitalized cloud computing implementation costs	(16,236)	(18,846)
Accounts payable and accrued expenses	17,138	23,095
Accrued payroll and benefit cost	68,340	12,067
Employee deferred compensation plan obligations	46,236	7,485
Income taxes payable	22,110	43,723
Other assets and liabilities, net	5,110	6,755
Net cash flows provided by operating activities	233,472	425,942
CASH FLOWS FROM INVESTING ACTIVITIES:
Capital expenditures	(16,114)	(22,264)
Investments in employee deferred compensation trusts	(42,423)	(49,098)
Proceeds from employee deferred compensation trust redemptions	27,424	28,347
Net cash flows used in investing activities	(31,113)	(43,015)
CASH FLOWS FROM FINANCING ACTIVITIES:
Repayment of notes payable	(117)	(107)
Repurchases of common stock	(145,314)	(69,977)
Dividends paid	(86,479)	(78,916)
Net cash flows used in financing activities	(231,910)	(149,000)
Effect of exchange rate fluctuations	(2,070)	(2,920)
Change in cash and cash equivalents	(31,621)	231,007
Cash and cash equivalents at beginning of period	574,426	270,478
Cash and cash equivalents at end of period	542,805	501,485
Non-cash items:
Stock repurchases awaiting settlement	1,345	0
Fund exchanges within employee deferred compensation trusts	$ 63,154	$ 160,028