Income Taxes (Components of Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Deferred tax assets:
Accruals and reserves	$ 36,628	$ 27,105
Deferred revenue	84,631	65,541
Tax credits	41,444	43,211
Net operating losses	50,466	75,318
Other	7,527	12,878
Stock based compensation	46,582	63,993
Valuation allowance	(16,673)	(15,167)
Total deferred tax assets	250,605	272,879
Deferred tax liabilities:
Depreciation and amortization	(16,113)	(16,835)
Acquired technology	(15,825)	(82,357)
Prepaid expenses	(7,374)	(9,372)
Total deferred tax liabilities	(39,312)	(108,564)
Total net deferred tax assets	$ 211,293	$ 164,315