Income Taxes (Details) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Schedule of Collaborative Arrangement Agreements [Line Items]
(Benefit from) provision for income taxes	$ (12,659,000)	$ 3,985,000
Excess tax benefits related to stock-based compensation	21,900,000
Tax provision attributable to noncontrolling interest	6,400,000
Unrecognized tax benefits	4,800,000		$ 3,800,000
Income taxes, interest and penalties accrued	0
Increase in unrecognized tax benefits is reasonably possible	0
Income taxes, material interest or penalties related to uncertain tax positions	0		0
Deferred tax asset subject to valuation allowance			$ 1,600,000,000
Deferred tax assets, valuation allowance	204,700,000
Variable Interest Entity, Primary Beneficiary
Schedule of Collaborative Arrangement Agreements [Line Items]
(Benefit from) provision for income taxes	6,405,000	$ 391,000
Income tax liability associated with variable interest entity	$ 0