Equity Instruments and Stock Based Compensation - Stock Options (Details) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($) $ / shares shares
Stock Options, Outstanding [Roll Forward]
Stock options outstanding, beginning balance (in shares) | shares	5,041
Granted (in shares) | shares	138
Exercised (in shares) | shares	(82)
Forfeited (in shares) | shares	(428)
Expired (in shares) | shares	(68)
Stock options outstanding, ending balance (in shares) | shares	4,601
Stock options exercisable (in shares) | shares	3,005
Stock Options, Outstanding, Weighted Average Exercise Price [Abstract]
Stock options outstanding, beginning balance (in usd per share) | $ / shares	$ 11.34
Granted (in usd per share) | $ / shares	6.67
Exercised (in usd per share) | $ / shares	6.52
Forfeited (in usd per share) | $ / shares	10.04
Expired (in usd per share) | $ / shares	12.41
Stock options outstanding, ending balance (in usd per share) | $ / shares	11.39
Stock options exercisable (in usd per share) | $ / shares	$ 11.99
Stock options outstanding, Weighted Average Remaining Contractual Life (in years)	7 years 3 months
Stock options exercisable, Weighted Average Remaining Contractual Life (in years)	6 years 7 months 28 days
Stock options outstanding, Aggregate Intrinsic Value | $	$ 0
Stock options exercisable, Aggregate Intrinsic Value | $	$ 0