Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Operating Activities:
Net earnings	$ 316,974	$ 184,188	$ 604,924	$ 306,970
Adjustments to reconcile net earnings to net cash from operating activities:
Provisions for losses on accounts receivable	1,090	2,389	2,289	4,209
Deferred income tax expense	1,850	9,287	10,001	4,148
Stock compensation expense	30,909	21,638	42,094	32,794
Depreciation and amortization	12,675	14,109	25,662	26,769
Other, net	346	118	897	551
Changes in operating assets and liabilities:
Increase in accounts receivable	(410,783)	(185,055)	(663,697)	(168,375)
Increase in accounts payable and accrued expenses	100,118	106,760	333,271	107,677
Increase in deferred contract costs	(150,382)	(2,333)	(221,640)	(18,401)
Increase (decrease) in contract liabilities	174,504	(595)	254,094	20,606
(Decrease) increase in income taxes payable, net	(47,994)	20,154	(1,356)	30,642
Decrease (increase) in other, net	1,164	16,061	(324)	4,131
Net cash from operating activities	30,471	186,721	386,215	351,721
Investing Activities:
Purchase of property and equipment	(6,539)	(22,114)	(14,930)	(28,241)
Other, net	138	(68)	104	(211)
Net cash from investing activities	(6,401)	(22,182)	(14,826)	(28,452)
Financing Activities:
Proceeds from issuance of common stock	22,711	29,187	42,468	52,586
Repurchases of common stock	(62,472)	(30,985)	(148,469)	(314,225)
Dividends paid	(98,387)	(86,815)	(98,387)	(86,815)
Payments for taxes related to net share settlement of equity awards	(13,893)	(9,170)	(15,168)	(10,566)
Net cash from financing activities	(152,041)	(97,783)	(219,556)	(359,020)
Effect of exchange rate changes on cash and cash equivalents	8,699	1,726	(5,503)	(14,285)
Change in cash and cash equivalents	(119,272)	68,482	146,330	(50,036)
Cash and cash equivalents at beginning of period	1,793,393	1,111,973	1,527,791	1,230,491
Cash and cash equivalents at end of period	1,674,121	1,180,455	1,674,121	1,180,455
Taxes Paid:
Income taxes	$ 143,959	$ 38,504	$ 190,536	$ 73,808