Business Segment Information (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2012 item
Business Segment Information [Abstract]
Number of nuclear power plants	6
Capital costs write off	$ 64,000,000
Debt financing costs write off	39,000,000
Spin-off credit facility	1,200,000,000
Other Noninterest Expense	$ 16,000,000