Commitments and Contingencies (Environmental) (Details) (USD $)				3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2013 Superfund sites Superfund_Sites	Mar. 31, 2013 Homer City Pennsylvania [Member]
Site Contingency [Line Items]
Penalty in excess of $100,000				$ 100,000
Accrual for Environmental Loss Contingencies Disclosure [Abstract]
Accrual for Environmental Loss Contingencies	71,000,000	72,000,000
Accrual for site contingency			$ 5,000,000
Number of superfund sites			9