CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Cash flows from operating activities:
Net income	$ 56,468	$ 56,132
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	17,432	19,428
Deferred income tax expense	8,676	7,116
Provision for bad debts	127	316
Stock-based compensation expense	7,078	7,831
Excess tax benefits from stock-based compensation	(2,148)	(2,582)
Other	(225)	(34)
Changes in operating assets and liabilities:
Accounts receivable	9,860	18,407
Other receivables and current assets	29,810	17,834
Other long-term assets	(92)	(238)
Accounts payable, accrued expenses and current liabilities	(32,258)	(36,971)
Accrued income taxes	14,602	9,634
Deferred revenue	5,387	19,734
Other long-term liabilities	(6,142)	(2,487)
Net cash provided by operating activities	108,575	114,120
Cash flows from investing activities:
Acquisitions, net of cash acquired	0	(10,477)
Capital expenditures	(2,695)	(3,622)
Other investing activities	4	(67)
Net cash used in investing activities	(2,691)	(14,166)
Cash flows from financing activities:
Principal payments on capital leases	(1)	(5)
Purchase of treasury stock	(42,684)	(125,627)
Restricted stock withholding taxes paid in lieu of issued shares	(4,752)	(4,243)
Contingent consideration payments	(1,048)	0
Proceeds from shares issued for stock-based compensation	10,136	15,770
Excess tax benefits from stock-based compensation	2,148	2,582
Net cash used in financing activities	(36,201)	(111,523)
Effect of exchange rate fluctuations on cash and cash equivalents	9,584	(16,101)
Net increase (decrease) in cash and cash equivalents	79,267	(27,670)
Cash and cash equivalents, beginning of period	784,168	788,064
Cash and cash equivalents, end of period	863,435	760,394
Supplemental disclosures of cash flow information:
Income taxes paid	6,037	3,273
Interest paid	$ 435	$ 22