Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement of Comprehensive Income [Abstract]
Net loss	$ (15,128)	$ (19,111)	$ (13,769)
Change in unrealized loss on investments	(258)	(86)	(60)
Change in minimum postretirement medical obligation	318	(1,066)	(1)
Change in unrealized loss on hedge contracts	0	(40)	(49)
Other comprehensive income (loss)	60	(1,192)	(110)
Total comprehensive loss	$ (15,068)	$ (20,303)	$ (13,879)