Income Taxes (Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets (liabilities):
Stock-based compensation	$ 190,451	$ 149,367
Depreciation and amortization	(151,678)	(70,382)
Federal and California tax R&D credits	369,023	260,686
Foreign tax credits	218,026	102,242
Accruals and reserves	36,396	34,170
Other	27,203	51,614
Gross deferred tax assets	689,421	527,697
Valuation allowance	(124,996)	(49,431)
Net deferred tax assets	$ 564,425	$ 478,266