Commitments And Contingencies (Environmental Remediation Contingencies) (Detail) (USD $)	Jun. 30, 2012	Dec. 31, 2011
Long-term Purchase Commitment [Line Items]
Amount of environmental loss accrual expected to be recovered	$ 573,000,000
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	210,000,000	149,000,000
Pacific Gas And Electric Company [Member]
Long-term Purchase Commitment [Line Items]
Utility undiscounted future costs	920,000,000	785,000,000
Increase in undiscounted future costs in the event other potentially responsible parties are not able to contribute	$ 1,600,000,000