Commitments And Contingencies (Environmental Remediation Contingencies) (Detail) (USD $)	Sep. 30, 2012	Dec. 31, 2011
Long-term Purchase Commitment [Line Items]
Amount of environmental loss accrual expected to be recovered	$ 550,000,000
Eligible resident households for voluntary program	300
Utility undiscounted future costs	150,000,000
Hinkley Natural Gas Compressor Station [Member]
Long-term Purchase Commitment [Line Items]
Utility undiscounted future costs	227,000,000	149,000,000
Topock Site [Member]
Long-term Purchase Commitment [Line Items]
Utility undiscounted future costs	236,000,000	218,000,000
Remediation cost recovery	90.00%
Pacific Gas And Electric Company [Member]
Long-term Purchase Commitment [Line Items]
Utility undiscounted future costs	913,000,000	785,000,000
Increase in undiscounted future costs in the event other potentially responsible parties are not able to contribute	$ 1,700,000,000