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		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Numerator:
Net loss	$ (45,677)	$ (63,475)	$ (63,393)	$ (123,007)
Less: noncumulative dividends to preferred stockholders	0	0	0	0
Less: undistributed earnings to participating securities	0	0	0	0
Net loss attributable to common stockholders - basic	(45,677)	(63,475)	(63,393)	(123,007)
Add: adjustments to undistributed earnings to participating securities	0	0	0	0
Net loss attributable to common stockholders - diluted	$ (45,677)	$ (63,475)	$ (63,393)	$ (123,007)
Denominator:
Weighted average shares of common stock-basic (in shares)	10,536	10,209	10,470	10,176
Effect of potentially dilutive stock options (in shares)	0	0	0	0
Weighted average shares of common stock-diluted (in shares)	10,536	10,209	10,470	10,176
Net loss per share attributable to common stockholders:
Net loss per share attributable to common stockholders, basic and diluted (in dollars per share)	$ (4.34)	$ (6.22)	$ (6.05)	$ (12.09)