Commitments And Contingencies (Third-Party Power Purchases) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Long-term Purchase Commitment [Line Items]
2012	$ 1,810
2013	2,860
2014	3,010
2015	3,007
2016	2,917
Thereafter	32,120
Total	45,724
Cost incurred by the Utility under power purchase agreements	435	587
Capital leases, future minimum lease payments	115
Total minimum lease payments terminated	$ 136
Minimum [Member]
Long-term Purchase Commitment [Line Items]
Long-term agreements range, years	10
Maximum [Member]
Long-term Purchase Commitment [Line Items]
Long-term agreements range, years	25