Fair Value Disclosure (Narrative) (Details) (USD $)				3 Months Ended	6 Months Ended
	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2013	Jun. 30, 2014 Reed Minerals	Jun. 30, 2014 Reed Minerals	Aug. 31, 2012 Reed Minerals T	Oct. 01, 2010 Bellaire Corporation
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of trust assets							$ 5,000,000
Tons of coal sold from reserves covered in earn-out period for earn-out calculation						15,000,000.0
Earn-out payments				0	0
Long-term debt excluding capital leases fair value	217,300,000	170,700,000	152,900,000
Long-term debt excluding capital leases book value	$ 217,300,000	$ 170,700,000	$ 152,500,000