Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets:
Net operating loss	$ 1,004,404	$ 1,232,399
Tax credit carryforwards	440,429	367,402
Intangible assets	54,091	34,938
Deferred revenues	19,593	31,205
Stock-based compensation	83,196	110,446
Inventories	4,250	4,705
Accrued expenses	17,808	23,078
Construction financing lease obligation	109,354	177,735
Other	1,417	27
Gross deferred tax assets	1,734,542	1,981,935
Valuation allowance	(1,552,942)	(1,731,186)
Total deferred tax assets	181,600	250,749
Deferred tax liabilities:
Property and equipment	(101,019)	(169,089)
Acquired intangibles	(6,341)	(134,063)
Deferred revenue	(73,357)	(73,357)
Unrealized gain	(6,401)	(7,967)
Net deferred tax liabilities	$ (5,518)	$ (133,727)