CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Cash flows from operating activities:
Net income	$ 285,443	$ 266,212
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and intangible assets amortization	42,216	47,341
Operating lease right-of-use assets amortization	13,912
Deferred income tax benefit	(13,221)	(28,175)
Provision for bad debts	2,559	1,389
Stock-based compensation expense	84,784	58,887
Other	2,560	2,039
Changes in operating assets and liabilities:
Accounts receivable	(12,610)	32,356
Other receivables and current assets	37,773	23,207
Other long-term assets	(2,288)	2,458
Accounts payable, accrued expenses and current liabilities	(37,289)	(31,243)
Accrued income taxes	(2,547)	(2,581)
Deferred revenue	(35,807)	1,175
Other long-term liabilities	(5,000)	(19,562)
Net cash provided by operating activities	360,485	353,503
Cash flows from investing activities:
Acquisitions, net of cash acquired	(294,987)	(283,026)
Capital expenditures	(25,781)	(13,077)
Other investing activities	(12,680)	(5,510)
Net cash used in investing activities	(333,448)	(301,613)
Cash flows from financing activities:
Purchase of treasury stock	(59,116)	(192,787)
Restricted stock withholding taxes paid in lieu of issued shares	(37,936)	(26,955)
Proceeds from shares issued for stock-based compensation	28,633	37,398
Other financing activities	(1,617)	(4,939)
Net cash used in financing activities	(70,036)	(187,283)
Effect of exchange rate fluctuations on cash and cash equivalents	(1,456)	(16,928)
Net decrease in cash and cash equivalents	(44,455)	(152,321)
Cash and cash equivalents, beginning of period	777,139	881,501
Cash and cash equivalents, end of period	732,684	729,180
Supplemental disclosure of cash flow information:
Income taxes paid	$ 73,561	$ 74,086