Nature of Business and Basis of Presentation Revision of Prior Period Amounts (Details) (USD $) In Thousands, unless otherwise specified	1 Months Ended		3 Months Ended								12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Cost of revenue			$ 133,951	$ 132,039	$ 124,705	$ 120,392	$ 139,494	$ 134,221	$ 131,260	$ 124,925	$ 511,087	$ 529,900	$ 453,705
Research and development											93,879	74,744	52,333
Sales and marketing											280,380	223,348	163,017
General and administrative											255,218	210,100	176,878
Amortization of acquired intangible assets											21,547	20,962	17,070
Restructuring charges	400	4,200									1,843	406	4,886
Total costs and operating expenses											1,163,954	1,059,460	867,889
Changes in operating assets and liabilities, net of effects of acquisitions and divestitures:
Prepaid expenses and other current assets											(3,842)	6,357	(4,828)
Accounts payable and accrued expenses											40,533	58,672	7,214
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:
Purchases of property and equipment											(187,964)	(166,773)	(133,445)
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
Net cash used in financing activities											(115,243)	(108,029)	(294,038)
Net (decrease) increase in cash and cash equivalents											131,902	(357,208)	327,331
As Previously Reported
Cost of revenue							111,893	109,995	107,457	102,566		431,911	374,543
Research and development												74,744	52,333
Sales and marketing												304,404	227,331
General and administrative												227,033	191,726
Amortization of acquired intangible assets												20,962	17,070
Restructuring charges												406	4,886
Total costs and operating expenses												1,059,460	867,889
Changes in operating assets and liabilities, net of effects of acquisitions and divestitures:
Prepaid expenses and other current assets												6,066	(7,014)
Accounts payable and accrued expenses												59,653	15,184
Other non-current assets and liabilities												(4,070)	8,704
Net cash provided by operating activities												530,405	452,555
Cash flows from investing activities:
Purchases of property and equipment												(165,642)	(140,218)
Other non-current assets and liabilities												(250)	272
Net cash (used in) provided by investing activities												(779,041)	171,123
Cash flows from financing activities:
Proceeds related to the issuance of common stock under stock plans												44,660	25,252
Net cash used in financing activities												(108,483)	(294,088)
Net (decrease) increase in cash and cash equivalents												(357,208)	327,331
Adjustment
Cost of revenue							27,601	24,226	23,803	22,359		97,989	79,162
Research and development												0	0
Sales and marketing												(81,056)	(64,314)
General and administrative												(16,933)	(14,848)
Amortization of acquired intangible assets												0	0
Restructuring charges												0	0
Total costs and operating expenses												0	0
Changes in operating assets and liabilities, net of effects of acquisitions and divestitures:
Prepaid expenses and other current assets												291	2,186
Accounts payable and accrued expenses												(981)	(7,970)
Other non-current assets and liabilities												305	(493)
Net cash provided by operating activities												(385)	(6,277)
Cash flows from investing activities:
Purchases of property and equipment												(1,131)	6,773
Other non-current assets and liabilities												1,062	(546)
Net cash (used in) provided by investing activities												(69)	6,227
Cash flows from financing activities:
Proceeds related to the issuance of common stock under stock plans												454	50
Net cash used in financing activities												454	50
Net (decrease) increase in cash and cash equivalents												$ 0	$ 0