Income Taxes (Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets (liabilities):
Stock-based compensation	$ 149,367	$ 188,458
Accruals and reserves	34,170	29,231
Depreciation and amortization	(70,382)	(93,760)
Federal and California tax R&D credits	260,686	107,283
Federal foreign tax credits	102,242	0
Other		(2,363)
Other	51,614
Gross deferred tax assets	527,697	228,849
Valuation allowance	(49,431)	(1,601)
Net deferred tax assets	$ 478,266	$ 227,248