Equity Instruments and Stock Based Compensation - Stock Options (Details) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($) $ / shares shares
Stock Options, Outstanding [Roll Forward]
Stock options outstanding, beginning balance (in shares) | shares	2,326
Granted (in shares) | shares	1,505
Exercised (in shares) | shares	(15)
Forfeited (in shares) | shares	(6)
Expired (in shares) | shares	(78)
Stock options outstanding, ending balance (in shares) | shares	3,732
Stock options exercisable (in shares) | shares	1,161
Stock Options, Outstanding, Weighted Average Exercise Price [Abstract]
Stock options outstanding, beginning balance (in usd per share) | $ / shares	$ 13.84
Granted (in usd per share) | $ / shares	10.68
Exercised (in usd per share) | $ / shares	6.50
Forfeited (in usd per share) | $ / shares	14.35
Expired (in usd per share) | $ / shares	31.70
Stock options outstanding, ending balance (in usd per share) | $ / shares	12.07
Stock options exercisable (in usd per share) | $ / shares	$ 10.49
Stock options outstanding, Weighted Average Remaining Contractual Life (years)	8 years 5 months 22 days
Stock options exercisable, Weighted Average Remaining Contractual Life (years)	6 years 9 months 2 days
Stock options outstanding, Aggregate Intrinsic Value | $	$ 3,681
Stock options exercisable, Aggregate Intrinsic Value | $	$ 3,035