Income Taxes (Details) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016	Mar. 31, 2017
Schedule of Collaborative Arrangement Agreements [Line Items]
(Benefit from) provision for income taxes	$ (125,903,000)	$ 503,000	$ (117,581,000)	$ 24,118,000
Unrecognized tax benefits	0		0		$ 0
Income taxes, interest and penalties accrued	0		0
Increase in unrecognized tax benefits is reasonably possible	0		0
Income taxes, material interest or penalties related to uncertain tax positions			0		0
Effective income tax rate reconciliation, share-based compensation, excess tax benefit, amount	31,400,000		62,200,000
Deferred tax asset subject to valuation allowance					1,700,000,000
Amount of unrecognized deferred tax liability, undistributed earnings of foreign subsidiaries	0		0
Accounting Standards Update 2016-09, Excess Tax Benefit
Schedule of Collaborative Arrangement Agreements [Line Items]
Operating loss carryforwards					410,800,000	$ 410,800,000
Deferred income tax assets, net					3,400,000
Retained Earnings | Accounting Standards Update 2016-09, Forfeiture Rate Component
Schedule of Collaborative Arrangement Agreements [Line Items]
Cumulative effect of new accounting principle in period of adoption					9,371,000
Variable Interest Entity, Primary Beneficiary
Schedule of Collaborative Arrangement Agreements [Line Items]
(Benefit from) provision for income taxes	(120,181,000)	$ (510,000)	(111,658,000)	$ 20,063,000
Income tax liability associated with variable interest entity	$ 0		$ 0
Internal Revenue Service (IRS)
Schedule of Collaborative Arrangement Agreements [Line Items]
Operating loss carryforwards					$ 4,100,000,000