Asset Acquisitions (Details) (USD $) In Millions, unless otherwise specified	Jun. 28, 2012
Asset Acquisitions
Consideration paid in the acquisition of the Young Creek Mining Company, LLC assets	$ 300

The value of all consideration given or received by the Entity in the significant acquisition or disposal.

No definition available.

Name:	us-gaap_SignificantAcquisitionsAndDisposalsAcquisitionCostsOrSaleProceeds
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant