Net Loss per Share Attributable to Common Stockholders - Schedule of Basic and Diluted Net Loss per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Numerator:
Net loss attributable to common stockholders	$ (78,579)	$ (71,831)	$ (141,972)	$ (194,838)
Less: noncumulative dividends to preferred stockholders		0
Less: undistributed earnings to participating securities	0	0	0	0
Net loss attributable to common stockholders (basic)	(78,579)	(71,831)	(141,972)	(194,838)
Add: adjustments to undistributed earnings to participating securities	0	0	0
Net loss attributable to common stockholders (diluted)	$ (78,579)	$ (71,831)	$ (141,972)	$ (194,838)
Denominator:
Weighted average shares of common stock (basic)	81,321	10,305	34,347	10,220
Effect of potentially dilutive stock options		0	0	0
Weighted average shares of common stock-diluted (in shares)	81,321	10,305	34,347
Net loss per share attributable to common stockholders:
Net loss per share attributable to common stockholders, basic and diluted (in dollars per share)	$ (0.97)	$ (6.97)	$ (4.13)	$ (19.06)