Restructuring and Asset Impairment (Details) (USD $)	3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2012	Sep. 30, 2012 North River mine	Sep. 30, 2012 North River mine	Sep. 30, 2012 Willow Creek mine	Sep. 30, 2012 Willow Creek mine	Sep. 30, 2013 North River Mine Closure	Sep. 30, 2013 Willow Creek Mine Closure
Asset impairment and restructuring
Gain on release of a below market contract liability							$ 17,000,000
Asset impairment charges	1,106,715,000	1,106,715,000	114,281,000	114,281,000	992,434,000	992,434,000	8,000,000
Curtailment costs								$ 10,700,000