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Commitments, Guarantees and Contingencies - Coal Rail and Shipping Contracts (Details) (Coal and Transportation [Member], USD $) In Millions, unless otherwise specified | Dec. 31, 2013
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Coal and Transportation [Member] |
Coal Rail and Shipping Contracts [Line Items] |
Coal Supply and Transportation Agreements, Minimum Annual Payment Obligation in 2014 | $ 35.3
Coal Supply and Transportation Agreements, Minimum Annual Payment Obligation in 2015 | $ 2.2

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- Definition Amount of the recorded unconditional purchase obligation maturing in the next fiscal year following the latest fiscal year. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 440 -SubTopic 10 -Section 50 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=6394976&loc=d3e25383-109308 + Details
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