Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating Activities:
Net earnings	$ 1,418,845	$ 698,214	$ 592,016
Adjustments to reconcile net earnings to net cash from operating activities:
Provisions for losses (recoveries) on accounts receivable	7,540	5,584	(1)
Deferred income tax (benefit) expense	(3,690)	8,371	4,482
Stock compensation expense	69,385	62,498	61,543
Depreciation and amortization	51,312	56,959	50,950
Other, net	3,790	3,960	941
Changes in operating assets and liabilities:
(Increase) decrease in accounts receivable	(1,869,827)	(647,193)	265,919
Increase (decrease) in accounts payable and accrued expenses	1,041,805	430,452	(182,233)
(Increase) decrease in deferred contract costs	(700,273)	(189,447)	28,811
Increase (decrease) in contract liabilities	803,837	217,699	(37,097)
Increase (decrease) in income taxes payable, net	57,867	8,502	(18,472)
(Increase) decrease in other, net	(12,097)	(630)	4,830
Net cash from operating activities	868,494	654,969	771,689
Investing Activities:
Purchase of property and equipment	(36,247)	(47,543)	(47,022)
Other, net	(398)	1,516	1,007
Net cash from investing activities	(36,645)	(46,027)	(46,015)
Financing Activities:
Proceeds from borrowing on lines of credit, net	7,512	43	246
Proceeds from issuance of common stock	106,105	186,345	148,245
Repurchases of common stock	(514,594)	(332,387)	(389,060)
Dividends paid	(195,766)	(174,929)	(170,553)
Payments for taxes related to net share settlement of equity awards	(15,172)	(10,566)	(6,674)
Distribution to noncontrolling interest	(1,631)	0	0
Net cash from financing activities	(613,546)	(331,494)	(417,796)
Effect of exchange rate changes on cash and cash equivalents	(17,402)	19,852	(1,122)
Change in cash and cash equivalents	200,901	297,300	306,756
Cash and cash equivalents at beginning of period	1,527,791	1,230,491	923,735
Cash and cash equivalents at end of period	1,728,692	1,527,791	1,230,491
Supplemental Cash Flow Information:
Cash paid for income taxes	$ 442,549	$ 239,849	$ 222,083