Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Cash flows from operating activities:
Net income	$ 293,487	$ 203,989	$ 200,904
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	184,431	204,163	167,878
Stock-based compensation	95,884	90,585	61,305
Provision for deferred income taxes	27,343	(5,819)	53,628
Provision for doubtful accounts	1,169	(316)	2,066
Excess tax benefits from stock-based compensation	(22,801)	(23,015)	(13,123)
Non-cash portion of restructuring charges	781	0	412
Loss on disposal of property and equipment	414	3	597
Gain from divestiture of a business	(1,188)	0	0
Changes in operating assets and liabilities, net of effects of acquisitions and divestitures:
Accounts receivable	(67,184)	(2,108)	(37,837)
Prepaid expenses and other current assets	(3,842)	6,357	(4,828)
Accounts payable and accrued expenses	40,533	58,672	7,214
Deferred revenue	11,495	4,552	(3,721)
Other current liabilities	52	(3,278)	3,572
Other non-current assets and liabilities	3,334	(3,765)	8,211
Net cash provided by operating activities	563,908	530,020	446,278
Cash flows from investing activities:
Cash paid for acquisitions, net of cash acquired	(30,657)	(336,680)	(550)
Purchases of property and equipment	(187,964)	(166,773)	(133,445)
Capitalization of internal-use software development costs	(72,109)	(54,204)	(42,644)
Purchases of short- and long-term marketable securities	(494,885)	(752,342)	(880,110)
Proceeds from sales and redemptions of short- and long-term marketable securities	160,210	214,277	701,313
Proceeds from maturities of short- and long-term marketable securities	314,925	315,788	532,910
Proceeds from sale of property and equipment	827	12	150
Other non-current assets and liabilities	3,455	(812)	274
Net cash (used in) provided by investing activities	(313,108)	(779,110)	177,350
Cash flows from financing activities:
Proceeds related to the issuance of common stock under stock plans	63,707	45,114	25,302
Excess tax benefits from stock-based compensation	22,801	23,015	13,123
Employee taxes paid related to net share settlement of stock-based awards	(41,332)	(34,690)	(8,393)
Repurchases of common stock	(160,419)	(141,468)	(324,070)
Net cash used in financing activities	(115,243)	(108,029)	(294,038)
Effects of exchange rate changes on cash and cash equivalents	(3,655)	(89)	(2,259)
Net increase (decrease) in cash and cash equivalents	131,902	(357,208)	327,331
Cash and cash equivalents at beginning of year	201,989	559,197	231,866
Cash and cash equivalents at end of year	333,891	201,989	559,197
Supplemental disclosure of cash flow information:
Cash paid for income taxes	63,508	94,833	45,578
Non-cash financing and investing activities:
Purchases of property and equipment and capitalization of internal-use software development costs included in accrued expenses	19,927	12,939	12,412
Capitalization of stock-based compensation	12,325	9,276	7,473
Convertible note receivable received for divestiture of a business	$ 18,882	$ 0	$ 0