Commitments and Contingencies Commitments and Contingencies - Hydroelectric Relicensing (Details) (USD $) In Millions, unless otherwise specified			9 Months Ended
	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2012 Klamath Hydroelectric System [Member]	Sep. 30, 2012 Klamath Hydroelectric System [Member] OREGON	Sep. 30, 2012 Klamath Hydroelectric System [Member] CALIFORNIA
Dam removal costs [Line Items]
Dam Removal Cost Limit			$ 200	$ 184	$ 16
Additional Dam Removal Costs, California Bond Measure			250
Assets	$ 21,570	$ 21,106	$ 118