Derivative Financial Instruments - Changes in Outstanding Warrants (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Changes in derivative instrument liability
Balance at the beginning of the period				$ 322					$ 322
Change in fair value of warrants during the quarter	$ 45	$ 87	$ 23	$ (260)	$ 30	$ (1,446)	$ 1,542	$ 268	(106)	$ 394	$ (1,362)
Balance at the end of the period	$ 216				$ 322				$ 216	$ 322
Derivative instrument liability
Changes in warrants
Beginning balance of warrants outstanding (in shares)				210,000				858,469	210,000	858,469
Expiration of warrants (in shares)					(292,000)	(2,469)	(324,000)
Exercise of warrants (in shares)					0	(30,000)
Ending balance of warrants outstanding (in shares)	210,000				210,000				210,000	210,000	858,469
Changes in derivative instrument liability
Balance at the beginning of the period				$ 322				$ 172	$ 322	$ 172
Change in fair value of warrants during the quarter	$ 45	$ 87	$ 22	$ (260)	$ (30)	$ 1,445	$ (1,541)	$ (268)
Expiration of warrants					(241)	$ (3)
Balance at the end of the period	$ 216				$ 322				$ 216	$ 322	$ 172