Commitments, Guarantees and Contingencies - Coal, Rail and Shipping Contracts (Details) (Coal and Transportation [Member], USD $) In Millions, unless otherwise specified	Jun. 30, 2014
Coal and Transportation [Member]
Coal, Rail and Shipping Contracts [Line Items]
Minimum Annual Payment Obligation, Current Year	$ 17.7
Minimum Annual Payment Obligation, Year Two	$ 4.0

Amount of the recorded unconditional purchase obligation maturing in the second fiscal year following the latest fiscal year.

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

Name:	us-gaap_RecordedUnconditionalPurchaseObligationDueInSecondYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant