Basis of Presentation and Summary of Significant Accounting Policies - Basic and diluted net income (loss) per share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Basic net (loss) income per common share calculation:
Net (loss) income	$ (13,068)	$ (6,106)	$ (29,351)	$ 28,201
Net (loss) income attributable to common stockholders	$ (17,192)	$ (9,385)	$ (41,699)	$ 18,365
Net (loss) income per share of common stock — basic (in USD per share)	$ (4.23)	$ (2.32)	$ (10.25)	$ 0.77
Diluted net (loss) income per common share calculation:
Net (loss) income	$ (13,068)	$ (6,106)	$ (29,351)	$ 28,201
Weighted average common shares outstanding — diluted (in shares)	4,067,717	4,050,065	4,067,717
Net (loss) income per share of common stock — diluted (in USD per share)	$ (4.23)	$ (2.32)	$ (10.25)	$ 0.63
Scenario, Adjustment
Basic net (loss) income per common share calculation:
Net (loss) income	$ (17,192)	$ (9,385)	$ (41,699)	$ 18,365
Less: undistributed earnings to participating securities	0	0	0	(15,253)
Net (loss) income attributable to common stockholders	$ (17,192)	$ (9,385)	$ (41,699)	$ 3,112
Weighted average common shares outstanding — basic (in shares)	4,067,717	4,050,065	4,067,717	4,049,800
Net (loss) income per share of common stock — basic (in USD per share)	$ (4.23)	$ (2.32)	$ (10.25)	$ 0.77
Diluted net (loss) income per common share calculation:
Net (loss) income	$ (17,192)	$ (9,385)	$ (41,699)	$ 18,365
Less: undistributed earnings to participating securities	0	0	0	(15,253)
Net (loss) income attributable to common stockholders — diluted	$ (17,192)	$ (9,385)	$ (41,699)	$ 3,112
Stock options (in shares)	0	0	0	925,212
Weighted average common shares outstanding — diluted (in shares)	4,067,717	4,050,065	4,067,717	4,975,012
Net (loss) income per share of common stock — diluted (in USD per share)	$ (4.23)	$ (2.32)	$ (10.25)	$ 0.63