Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Operating Activities:
Net earnings	$ 359,910	$ 191,719	$ 964,834	$ 498,689
Adjustments to reconcile net earnings to net cash from operating activities:
Provisions for losses on accounts receivable	3,739	398	6,028	4,607
Deferred income tax (benefit) expense	(7,658)	(1,276)	2,343	2,872
Stock compensation expense	15,204	12,297	57,298	45,091
Depreciation and amortization	12,753	15,851	38,415	42,620
Other, net	626	2,919	1,523	3,470
Changes in operating assets and liabilities:
Increase in accounts receivable	(714,300)	(106,065)	(1,377,997)	(274,440)
Increase in accounts payable and accrued liabilities	436,343	94,232	769,525	201,929
Increase in deferred contract costs	(328,932)	(81,486)	(550,572)	(99,887)
Increase in contract liabilities	381,192	91,638	635,286	112,244
Increase (decrease) in income taxes payable, net	33,378	(41,286)	32,022	(10,644)
Increase in other, net	(14,884)	(17,373)	(15,208)	(13,242)
Net cash from operating activities	177,371	161,568	563,497	513,309
Investing Activities:
Purchase of property and equipment	(9,870)	(9,178)	(24,800)	(37,419)
Other, net	(157)	1,174	(53)	963
Net cash from investing activities	(10,027)	(8,004)	(24,853)	(36,456)
Financing Activities:
Proceeds from borrowing on lines of credit, net	7,479	31	7,568	11
Proceeds from issuance of common stock	56,965	121,430	99,433	174,016
Repurchases of common stock	(76,595)		(225,064)	(314,225)
Dividends paid			(98,387)	(86,815)
Payments for taxes related to net share settlement of equity awards	(4)		(15,172)	(10,566)
Distribution to noncontrolling interest	(1,631)		(1,631)
Net cash from financing activities	(13,786)	121,461	(233,253)	(237,579)
Effect of exchange rate changes on cash and cash equivalents	(7,573)	10,030	(13,076)	(4,255)
Change in cash and cash equivalents	145,985	285,055	292,315	235,019
Cash and cash equivalents at beginning of period	1,674,121	1,180,455	1,527,791	1,230,491
Cash and cash equivalents at end of period	1,820,106	1,465,510	1,820,106	1,465,510
Taxes Paid:
Income taxes	$ 104,617	$ 106,434	$ 295,153	$ 180,242