Warrants, Restricted Stock, Restricted Stock Units, Options and Option Matching Rights - Options and Equity Incentive Plan (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Mar. 08, 2016	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options outstanding (in shares)	13,300	33,600	56,600		156,200
Stock-based compensation expense	$ 2,800	$ 2,722	$ 596
Total unrecognized compensation	$ 1,700
Vesting period for unrecognized compensation cost to be recognized (in years)	2 years 6 months	2 years 6 months
Proceeds from stock options exercised	$ 16	$ 54	$ 200
Second Amended And Restated 2005 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options outstanding (in shares)		13,300
Options exercisable (in shares)		13,300
2015 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized (in shares)		2,425,934		2,600,707