Nature of Business and Basis of Presentation Revision of Prior Period Amounts (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Cost of revenue	$ 132,039	$ 134,221	$ 377,136	$ 390,406
Research and development	24,857	19,351	67,359	54,373
Sales and marketing	67,811	55,206	198,326	160,681
General and administrative	66,634	51,003	183,365	156,241
Amortization of acquired intangible assets	4,859	5,381	16,653	15,611
Restructuring charges	69	0	891	14
Total costs and operating expenses	296,269	265,162	843,730	777,326
Adjustments to reconcile net income to net cash provided by operating activities:
Prepaid expenses and other current assets			(9,266)	10,010
Accounts payable and accrued expenses			43,730	49,149
Other non-current assets and liabilities			(3,328)	(104)
Net cash provided by operating activities			392,176	377,307
Purchases of property and equipment			(142,567)	(119,116)
Other non-currents assets and liabilities			(3,320)	979
Net cash used in investing activities			(286,571)	(668,227)
Proceeds related to the issuance of common stock under stock plans			54,418	33,760
Net cash used in financing activities			(68,397)	(86,866)
Net decrease in cash and cash equivalents			33,026	(376,547)
As previously reported [Member]
Cost of revenue		109,995		320,018
Research and development		19,351		54,373
Sales and marketing		75,924		219,096
General and administrative		54,511		168,214
Amortization of acquired intangible assets		5,381		15,611
Restructuring charges		0		14
Total costs and operating expenses		265,162		777,326
Adjustments to reconcile net income to net cash provided by operating activities:
Prepaid expenses and other current assets				11,103
Accounts payable and accrued expenses				54,732
Other non-current assets and liabilities				(536)
Net cash provided by operating activities				383,551
Purchases of property and equipment				(119,256)
Other non-currents assets and liabilities				0
Net cash used in investing activities				(669,346)
Proceeds related to the issuance of common stock under stock plans				28,635
Net cash used in financing activities				(91,991)
Net decrease in cash and cash equivalents				(376,547)
Adjustment [Member]
Cost of revenue		24,226		70,388
Research and development		0		0
Sales and marketing		(20,718)		(58,415)
General and administrative		(3,508)		(11,973)
Amortization of acquired intangible assets		0		0
Restructuring charges		0		0
Total costs and operating expenses		0		0
Adjustments to reconcile net income to net cash provided by operating activities:
Prepaid expenses and other current assets				(1,093)
Accounts payable and accrued expenses				(5,583)
Other non-current assets and liabilities				432
Net cash provided by operating activities				(6,244)
Purchases of property and equipment				140
Other non-currents assets and liabilities				979
Net cash used in investing activities				1,119
Proceeds related to the issuance of common stock under stock plans				5,125
Net cash used in financing activities				5,125
Net decrease in cash and cash equivalents				$ 0