Income Taxes - Effective Income Tax Reconciliation (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of Income Tax Expense:
Loss before (benefit from) provision for income taxes	$ 112,442	$ (417,170)	$ 35,506	$ 253,533	$ 20,306	$ (39,034)	$ (18,021)	$ (30,617)	$ (15,689)	$ (67,366)	$ (557,800)
Expected benefit from income taxes									(5,491)	(23,578)	(195,230)
State taxes, net of federal benefit									4,742	3,621	3,800
Foreign income tax rate differential									77,801	21,346	47,402
Tax credits									(49,088)	(47,773)	(55,696)
Provision for (benefit from) income taxes attributable to valuation allowances									(584,917)	14,837	226,169
Permanent items									21,825	24,749	5,817
Rate change									575,192	12,836	(1,224)
Stock compensation (benefit) shortfalls and cancellations									(21,453)	4,162	951
Tax attribute expiration									0	9,947	0
Deconsolidation of VIE									(126,183)	0	0
Other									248	(3,482)	(1,608)
(Benefit from) provision for income taxes	$ 10,257	$ (125,903)	$ 4,337	$ 3,985	$ (7,453)	$ 503	$ 18,130	$ 5,485	$ (107,324)	$ 16,665	$ 30,381