SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Revenues Disaggregated by Type of Customer) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenue from contracts with customers
Total operating revenues	$ 4,381	$ 4,517	$ 12,671	$ 13,035
Electric
Revenue from contracts with customers
Total operating revenues	3,466	3,648	9,729	10,036
Natural gas
Revenue from contracts with customers
Total operating revenues	915	869	2,942	2,999
Pacific Gas & Electric Co
Revenue from contracts with customers
Total operating revenues	4,382	4,516	12,672	13,037
Pacific Gas & Electric Co | Electric
Revenue from contracts with customers
Total revenue from contracts with customers	3,795		9,519
Regulatory balancing accounts	(328)		211
Total operating revenues	3,467	3,647	9,730	10,038
Pacific Gas & Electric Co | Electric | Residential
Revenue from contracts with customers
Total revenue from contracts with customers	1,649		4,023
Pacific Gas & Electric Co | Electric | Commercial
Revenue from contracts with customers
Total revenue from contracts with customers	1,430		3,737
Pacific Gas & Electric Co | Electric | Industrial
Revenue from contracts with customers
Total revenue from contracts with customers	448		1,126
Pacific Gas & Electric Co | Electric | Agricultural
Revenue from contracts with customers
Total revenue from contracts with customers	523		966
Pacific Gas & Electric Co | Electric | Public street and highway lighting
Revenue from contracts with customers
Total revenue from contracts with customers	18		55
Pacific Gas & Electric Co | Electric | Other
Revenue from contracts with customers
Total revenue from contracts with customers	(273)		(388)
Pacific Gas & Electric Co | Natural gas
Revenue from contracts with customers
Total revenue from contracts with customers	646		2,752
Regulatory balancing accounts	269		190
Total operating revenues	915	$ 869	2,942	$ 2,999
Pacific Gas & Electric Co | Natural gas | Residential
Revenue from contracts with customers
Total revenue from contracts with customers	242		1,652
Pacific Gas & Electric Co | Natural gas | Commercial
Revenue from contracts with customers
Total revenue from contracts with customers	87		402
Pacific Gas & Electric Co | Natural gas | Transportation service only
Revenue from contracts with customers
Total revenue from contracts with customers	287		847
Pacific Gas & Electric Co | Natural gas | Other
Revenue from contracts with customers
Total revenue from contracts with customers	$ 30		$ (149)