Environmental and Legal Contingencies (Details 4) (USD $) In Millions, unless otherwise specified	12 Months Ended	3 Months Ended	0 Months Ended
	Dec. 31, 2005 Schumacher [Member] plaintiffs	Mar. 31, 2014 Antitrust Case [Member]	Mar. 28, 2010 Heritage Coal [Member]	Mar. 06, 2014 Attorneys [Member] Final [Member] Schumacher [Member]	Oct. 14, 2013 Attorneys [Member] Final [Member] Schumacher [Member]	Nov. 21, 2013 Interest Included [Member] Final [Member] Schumacher [Member]	Jul. 31, 2013 CHINA Final [Member] MOFCOM [Member]	Jul. 31, 2013 CHINA Countervailing Duty [Member] Preliminary [Member] MOFCOM [Member]	Mar. 05, 2014 CHINA Countervailing Duty [Member] Preliminary [Member] US Trade Case - GOES [Member]	Mar. 19, 2014 CHINA Countervailing Duty [Member] Preliminary [Member] US Trade Case - NOES [Member]	Jul. 31, 2013 CHINA Countervailing Duty [Member] Final [Member] MOFCOM [Member]	Jul. 31, 2013 CHINA Antidumping Duty [Member] Final [Member] MOFCOM [Member]	Mar. 19, 2014 Leicong Industrial Company [Member] TAIWAN, PROVINCE OF CHINA Countervailing Duty [Member] Preliminary [Member] US Trade Case - NOES [Member]	Mar. 19, 2014 All Other Producers [Member] TAIWAN, PROVINCE OF CHINA Countervailing Duty [Member] Preliminary [Member] US Trade Case - NOES [Member]
Loss Contingencies [Line Items]
Loss Contingency, Number of Plaintiffs	92
Potential exposure of increase to defined benefit plan obligation					$ 1.3
Gain (Loss) Related to Litigation Settlement		5.8
Loss Contingency, Damages Paid, Value			$ 0.2	$ 0.6		$ 4.4
Duty Rate							11.20%	11.70%	49.15%	125.83%	3.40%	7.80%	12.82%	6.41%