Mine Closure and Asset Impairment Costs (Narrative) (Details)	6 Months Ended
Jun. 30, 2012
Restructuring and Related Activities [Abstract]
Restructuring and Related Cost, Number of Positions Eliminated	750

The number of positions eliminated during the period as a result of restructuring activities.

No definition available.

Name:	us-gaap_RestructuringAndRelatedCostNumberOfPositionsEliminated
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration