Commitments and Contingencies Commitments and Contingencies - Hydroelectric Relicensing (Details) (USD $) In Millions, unless otherwise specified			12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012 Klamath Hydroelectric System [Member]	Dec. 31, 2012 OREGON Klamath Hydroelectric System [Member]	Dec. 31, 2012 CALIFORNIA Klamath Hydroelectric System [Member]
Dam removal costs [Line Items]
Dam removal cost limit			$ 200	$ 184	$ 16
Additional dam removal costs, California bond measure			250
Assets	$ 21,728	$ 21,106	$ 115