Stock-Based Compensation - Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Number of shares
Outstanding at beginning of period (in shares)	1,279,379
Granted (in shares)	295,000
Exercised (shares)	0
Forfeited (in shares)	(268,256)
Expired (in shares)	(189,773)
Outstanding at end of period (in shares)	1,116,350	1,279,379
Exercisable at end of period (in shares)	660,625
Weighted- average exercise price
Outstanding at beginning of period (in dollars per share)	$ 15.16
Granted (in dollars per share)	2.88
Exercised (in dollars per share)	0.00
Forfeited (in dollars per share)	9.62
Expired (in dollars per share)	14.43
Outstanding at end of period (in dollars per share)	13.38	$ 15.16
Exercisable at end of period (in dollars per share)	$ 20.20
Additional disclosures
Weighted-average remaining contractual term (in years), outstanding	7 years 4 months	7 years 2 months
Weighted-average remaining contractual term (in years), exercisable	6 years
Aggregate intrinsic value, outstanding	$ 236,576	$ 0
Aggregate intrinsic value, exercisable	$ 29,959