Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Operating Activities:
Net earnings	$ 122,782	$ 140,111
Adjustments to reconcile net earnings to net cash from operating activities:
Provisions for losses (recoveries) on accounts receivable	1,820	(1,888)
Deferred income tax (benefit) expense	(5,139)	2,108
Stock compensation expense	11,156	13,382
Depreciation and amortization	12,660	13,393
Other, net	433	189
Changes in operating assets and liabilities:
Decrease in accounts receivable	16,680	230,477
Increase (decrease) in accounts payable and accrued expenses	917	(122,283)
(Increase) decrease in deferred contract costs	(16,068)	31,259
Increase (decrease) in contract liabilities	21,201	(36,725)
Increase in income taxes payable, net	10,488	16,993
(Increase) decrease in other, net	(11,930)	2,467
Net cash from operating activities	165,000	289,483
Investing Activities:
Purchase of property and equipment	(6,127)	(9,435)
Other, net	(143)	255
Net cash from investing activities	(6,270)	(9,180)
Financing Activities:
Proceeds from issuance of common stock	23,399	27,190
Repurchases of common stock	(283,240)	(44,334)
Payments for taxes related to net share settlement of equity awards	(1,396)
Net cash from financing activities	(261,237)	(17,144)
Effect of exchange rate changes on cash and cash equivalents	(16,011)	2,535
Change in cash and cash equivalents	(118,518)	265,694
Cash and cash equivalents at beginning of period	1,230,491	923,735
Cash and cash equivalents at end of period	1,111,973	1,189,429
Taxes Paid:
Income taxes	$ 35,304	$ 37,253