Condensed Consolidated Statements Of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Operating Activities
Net income	$ 83,463	$ 28,887
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, amortization and other	70,961	74,081
Stock-based compensation expense	42,097	34,211
Excess tax benefit from stock-based compensation	(5,889)	(1,151)
Deferred income tax expense	4,830	19,013
Effects of exchange rate changes on monetary assets and liabilities denominated in foreign currencies	(1,454)	10,007
Other non-cash items	2,641	3,490
Total adjustments to reconcile net income to net cash provided by operating activities	113,186	139,651
Changes in operating assets and liabilities, net of the effects of acquisitions:
Accounts receivable	219,570	231,034
Inventories	(2,072)	319
Prepaid expenses and other current assets	(29,115)	(7,313)
Other assets	750	(9,185)
Income taxes, net	1,602	(18,954)
Accounts payable	(14,559)	1,883
Accrued expenses and other current liabilities	2,919	(34,405)
Deferred revenues	(37,402)	(41,840)
Other liabilities	1,623	1,794
Total changes in operating assets and liabilities, net of the effects of acquisitions	143,316	123,333
Net cash provided by operating activities	339,965	291,871
Investing Activities
Purchases of available-for-sale investments	(466,718)	(556,484)
Proceeds from sales of available-for-sale investments	234,242	432,908
Proceeds from maturities of available-for-sale investments	139,244	161,429
Purchases of property and equipment	(41,550)	(44,091)
Cash paid for acquisitions, net of cash acquired	0	(89,467)
Cash paid for licensing agreements and technology	(24,281)	(2,082)
Other	1,008	(737)
Net cash used in investing activities	(158,055)	(98,524)
Financing Activities
Proceeds from issuance of common stock under stock-based compensation plans	6,024	8,413
Proceeds from credit facility	0	95,000
Repayment of acquired debt	0	(3,175)
Excess tax benefit from stock-based compensation	5,889	1,151
Stock repurchases, net	(28,689)	(124,928)
Cash paid for tax withholding on vested stock awards	(22,428)	(19,394)
Net cash used in financing activities	(39,204)	(42,933)
Effect of exchange rate changes on cash and cash equivalents	2,082	(7,630)
Change in cash and cash equivalents	144,788	142,784
Cash and cash equivalents at beginning of period	368,518	260,149
Cash and cash equivalents at end of period	$ 513,306	$ 402,933