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	Sep. 30, 2017	Dec. 31, 2016
Employee Stock Option [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Options, grants in period, weighted average grant date fair value (in dollars per share)	$ 3.04
Options outstanding rollforward
Outstanding at January 1, 2017 (in shares)	3,204,622	3,420,385	3,204,622	3,420,385
Granted (in shares)	460,566
Exercised (in shares)	(183,460)
Forfeited (in shares)	(438,004)
Expired (in shares)	(54,865)
Outstanding at June 30, 2017 (in shares)	3,204,622	3,420,385
Exercisable at June 30, 2017 (in shares)			2,596,301
Options, weighted average exercise price
Outstanding at January 1, 2017 (in dollars per share)			$ 6.37	$ 6.26
Granted (in dollars per share)	$ 6.22
Exercised (in dollars per share)	5.03
Forfeited (in dollars per share)	6.09
Expired (in dollars per share)	$ 4.90
Exercisable at June 30, 2017 (in dollars per share)			$ 6.51
Options Intrinsic Value
Options outstanding at January 1, 2017, intrinsic value (in dollars per share)	$ 1,204
Options, exercised, intrinsic value (in dollars per share)	253
Options outstanding at June 30, 2017, intrinsic value (in dollars per share)	$ 2,459	$ 1,204
Options exercisable, at June 30, 2017, intrinsic value (in dollars per share)			$ 1,730
Options additional disclosures
Outstanding weighted average remaining contractual term (in years)	4 years 1 month 6 days	4 years 3 months 18 days
Weighted average remaining contractual term, options exercisable (in dollars per share)	3 years 6 months
Equity Incentive Plan [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Stock options expiration period	7 years
Employee Group [Member]
Options outstanding rollforward
Granted (in shares)	335,000
Employee Group [Member] | Equity Incentive Plan [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Stock options vesting period	3 years
Director [Member]
Options outstanding rollforward
Granted (in shares)	125,566
Director [Member] | Equity Incentive Plan [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Stock options vesting period	1 year