Fair Value Measurements (Carrying Amount And Fair Value Of Financial Instruments) (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Carrying Amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt financial instrument	$ 349	$ 349
Energy recovery bonds (Note 4)	223	423
Pacific Gas And Electric Company [Member] | Carrying Amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt financial instrument	10,894	10,545
Fair Value Measurements, Level 2 [Member] | Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt financial instrument	377	380
Energy recovery bonds (Note 4)	226	433
Fair Value Measurements, Level 2 [Member] | Pacific Gas And Electric Company [Member] | Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt financial instrument	$ 13,173	$ 12,543