Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Operating Activities:
Net earnings	$ 93,567	$ 97,047
Adjustments to reconcile net earnings to net cash from operating activities:
Provision for losses on accounts receivable	931	578
Deferred income tax expense	5,593	9,896
Stock compensation expense	10,623	10,831
Depreciation and amortization	11,927	11,329
Other, net	(351)	36
Changes in operating assets and liabilities:
Decrease in accounts receivable	75,454	112,710
Decrease in accounts payable and accrued expenses	(18,324)	(15,344)
Increase in income taxes payable, net	19,824	10,925
Increase in other current assets	(3,565)	(2,055)
Net cash from operating activities	195,679	235,953
Investing Activities:
Purchase of property and equipment	(12,761)	(14,035)
Other, net	(671)	(559)
Net cash from investing activities	(13,432)	(14,594)
Financing Activities:
Proceeds from issuance of common stock	45,365	41,635
Repurchases of common stock	(53,908)	(70,292)
Net cash from financing activities	(8,543)	(28,657)
Effect of exchange rate changes on cash and cash equivalents	7,904	13,419
Increase in cash and cash equivalents	181,608	206,121
Cash and cash equivalents at beginning of period	974,435	807,796
Cash and cash equivalents at end of period	1,156,043	1,013,917
Taxes Paid:
Income taxes	$ 29,146	$ 37,984