Other Long-Term Assets and Other Income (Schedule of Other Income) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Other income:
MSHA reimbursements	[1]			$ 3,672
Coal storage fees		$ 600	$ 383	1,238
Miscellaneous		1,636	1,366	768
Other income		$ 2,236	$ 1,749	$ 5,678

[1] See “MSHA Reimbursements” in the MD&A section for a discussion of these amounts.