Stock-based Compensation - Performance-based stock options (Details) - Performance Based Stock Options - $ / shares	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Performance-based stock options activity
Shares outstanding, beginning (in shares)	2,171,760
Granted (in shares)	0
Exercised (in shares)	0
Forfeited (in shares)	0
Shares outstanding, ending (in shares)	2,171,760	2,171,760
Exercisable at September 30, 2017 (in shares)	1,016,600
Performance-based stock options weighted average exercise price
Beginning balance, Weighted average exercise price (in dollars per share)	$ 9.59
Granted, Weighted average exercise price (in dollars per share)	0.00
Exercised, Weighted average exercise price (in dollars per share)	0.00
Forfeited, Weighted average exercise price (in dollars per share)	0.00
Ending balance, Weighted average exercise price (in dollars per share)	9.59	$ 9.59
Options exercisable, Weighted average exercise price per share (in dollars per share)	$ 1.96
Performance-based stock options, additional disclosures
Options outstanding, Weighted average remaining contractual life	5 years 8 months 27 days	6 years 6 months 18 days
Options exercisable,Weighted average remaining contractual life	4 years 29 days