Employee Benefit Plans - Stock Options Rollforward (Details) - USD ($) $ / shares in Units, shares in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Options
Balance, December 31, 2015, shares	3,897
Granted, shares	155
Exercised, shares	(50)
Forfeited, shares	(447)
Expired, shares	(392)
Balance, December 31, 2016, shares	3,163
Options exercisable at December 31, 2016, shares	2,648
Options vested as of December 31, 2016 and expected to vest after December 31, 2016, shares	3,163
Weighted Average Exercise Price
Balance, December 31, 2015 (usd per share)	$ 3.81
Granted (usd per share)	1.15
Exercised (usd per share)	2.38
Forfeited (usd per share)	4.16
Expired (usd per share)	5.85
Balance, December 31, 2016 (usd per share)	3.40
Options exercisable at December 31, 2016 (usd per share)	3.48
Options vested as of December 31, 2016 and expected to vest after December 31, 2016 (usd per share)	$ 3.40
Aggregate Intrinsic Value	$ 26,000	$ 3,642,000
Options exercisable aggregate intrinsic value	4
Options vested and expected to vest at year end aggregate intrinsic value	$ 26,000