Long-term Debt Principal payments under the Energy Credit Agreement (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Debt Disclosure [Abstract]
2016	$ 0
2017	3,303
2018	39,643
Total	42,946
Less current portion	0	$ 13,157
Unamortized debt issuance costs - long-term	280	575
Total long-term debt	$ 42,666	$ 65,496