Income Taxes - Schedule of Change in Valuation Allowance (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Deferred Tax Assets, Net of Valuation Allowance [Abstract]
Valuation allowance, at beginning of year	$ 115,689	$ 84,167	$ 64,449
Valuation allowance, at beginning of year, as adjusted	115,689	102,126	64,449
Increase in valuation allowance, excluding Tax Act impact	45,512	13,563	19,718
Decrease in valuation allowance - federal tax rate change	(52,757)	0	0
Release of valuation allowance due to the Tax Act	(1,398)	0	0
Valuation allowance, at end of year	107,046	115,689	84,167
Valuation Allowance of Deferred Tax Assets
Deferred Tax Assets, Net of Valuation Allowance [Abstract]
Increase in valuation allowance- share-based compensation guidance impact	$ 0	$ 17,959	$ 0