Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Operating Activities:
Net earnings	$ 191,719	$ 160,627	$ 498,689	$ 454,268
Adjustments to reconcile net earnings to net cash from operating activities:
Provisions for losses on accounts receivable	398	757	4,607	453
Deferred income tax (benefit) expense	(1,276)	(5,822)	2,872	(17)
Stock compensation expense	12,297	12,155	45,091	49,361
Depreciation and amortization	15,851	12,386	42,620	38,456
Other, net	2,919	652	3,470	812
Changes in operating assets and liabilities:
(Increase) decrease in accounts receivable	(106,065)	43,885	(274,440)	246,175
Increase (decrease) in accounts payable and accrued expenses	94,263	(58,816)	201,940	(141,199)
(Increase) decrease in deferred contract costs	(81,486)	10,301	(99,887)	28,550
Increase (decrease) in contract liabilities	91,638	(13,211)	112,244	(36,933)
(Decrease) in income taxes payable, net	(41,286)	(671)	(10,644)	(33,284)
(Increase) decrease in other, net	(17,373)	(744)	(13,242)	47
Net cash from operating activities	161,599	161,499	513,320	606,689
Investing Activities:
Purchase of property and equipment	(9,178)	(15,521)	(37,419)	(37,943)
Other, net	1,174	232	963	1,525
Net cash from investing activities	(8,004)	(15,289)	(36,456)	(36,418)
Financing Activities:
Proceeds from issuance of common stock	121,430	60,713	174,016	120,190
Repurchases of common stock		(61,999)	(314,225)	(296,922)
Dividends paid			(86,815)	(85,184)
Payments for taxes related to net share settlement of equity awards			(10,566)	(6,674)
Net cash from financing activities	121,430	(1,286)	(237,590)	(268,590)
Effect of exchange rate changes on cash and cash equivalents	10,030	(11,604)	(4,255)	(9,446)
Change in cash and cash equivalents	285,055	133,320	235,019	292,235
Cash and cash equivalents at beginning of period	1,180,455	1,082,650	1,230,491	923,735
Cash and cash equivalents at end of period	1,465,510	1,215,970	1,465,510	1,215,970
Taxes Paid:
Income taxes	$ 106,434	$ 61,201	$ 180,242	$ 196,169