Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Operating Activities:
Net earnings	$ 287,950	$ 122,782
Adjustments to reconcile net earnings to net cash from operating activities:
Provisions for losses on accounts receivable	1,199	1,820
Deferred income tax expense (benefit)	8,151	(5,139)
Stock compensation expense	11,185	11,156
Depreciation and amortization	12,987	12,660
Other, net	551	433
Changes in operating assets and liabilities:
(Increase) decrease in accounts receivable	(252,914)	16,680
Increase in accounts payable and accrued expenses	233,153	917
Increase in deferred contract costs	(71,258)	(16,068)
Increase in contract liabilities	79,590	21,201
Increase in income taxes payable, net	46,638	10,488
Increase in other, net	(1,488)	(11,930)
Net cash from operating activities	355,744	165,000
Investing Activities:
Purchase of property and equipment	(8,391)	(6,127)
Other, net	(34)	(143)
Net cash from investing activities	(8,425)	(6,270)
Financing Activities:
Proceeds from issuance of common stock	19,757	23,399
Repurchases of common stock	(85,997)	(283,240)
Payments for taxes related to net share settlement of equity awards	(1,275)	(1,396)
Net cash from financing activities	(67,515)	(261,237)
Effect of exchange rate changes on cash and cash equivalents	(14,202)	(16,011)
Change in cash and cash equivalents	265,602	(118,518)
Cash and cash equivalents at beginning of period	1,527,791	1,230,491
Cash and cash equivalents at end of period	1,793,393	1,111,973
Taxes Paid:
Income taxes	$ 46,607	$ 35,304