CONTINGENCIES AND COMMITMENTS (Environmental Remediation Contingencies) (Details) $ in Millions	Mar. 31, 2018 USD ($)
Long-term Purchase Commitment [Line Items]
Recorded third-party environmental recoveries receivable	$ 737
Topock Site
Long-term Purchase Commitment [Line Items]
Utility undiscounted future costs	293
Hinkley Natural Gas Compressor Station
Long-term Purchase Commitment [Line Items]
Utility undiscounted future costs	146
Former Manufactured Gas Plant
Long-term Purchase Commitment [Line Items]
Utility undiscounted future costs	340
Utility Owned Generation Facilities and Third Party Disposal Sites
Long-term Purchase Commitment [Line Items]
Utility undiscounted future costs	142
Fossil Fuel Fired Generation
Long-term Purchase Commitment [Line Items]
Utility undiscounted future costs	$ 106
Pacific Gas & Electric Co | Topock Site
Long-term Purchase Commitment [Line Items]
Remediation cost recovery percentage	90.00%
Pacific Gas & Electric Co | Former Manufactured Gas Plant
Long-term Purchase Commitment [Line Items]
Remediation cost recovery percentage	90.00%
Pacific Gas & Electric Co | Utility Owned Generation Facilities and Third Party Disposal Sites
Long-term Purchase Commitment [Line Items]
Remediation cost recovery percentage	90.00%