SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Revenues Disaggregated by Type of Customer) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenue from contracts with customers
Total operating revenues	$ 18,469	$ 17,129	$ 16,759
Electric
Revenue from contracts with customers
Total operating revenues	13,858	12,740	12,713
Natural gas
Revenue from contracts with customers
Total operating revenues	4,611	4,389	4,046
Pacific Gas & Electric Co (Utility)
Revenue from contracts with customers
Total operating revenues	18,469	17,129	16,760
Pacific Gas & Electric Co (Utility) | Electric
Revenue from contracts with customers
Total operating revenues	13,185	12,437
Regulatory balancing accounts	673	303
Total operating revenues	13,858	12,740	12,713
Pacific Gas & Electric Co (Utility) | Electric | Residential
Revenue from contracts with customers
Total operating revenues	5,523	4,847
Pacific Gas & Electric Co (Utility) | Electric | Commercial
Revenue from contracts with customers
Total operating revenues	4,722	4,756
Pacific Gas & Electric Co (Utility) | Electric | Industrial
Revenue from contracts with customers
Total operating revenues	1,530	1,493
Pacific Gas & Electric Co (Utility) | Electric | Agricultural
Revenue from contracts with customers
Total operating revenues	1,471	1,106
Pacific Gas & Electric Co (Utility) | Electric | Public street and highway lighting
Revenue from contracts with customers
Total operating revenues	69	67
Pacific Gas & Electric Co (Utility) | Electric | Other
Revenue from contracts with customers
Total operating revenues	(130)	168
Pacific Gas & Electric Co (Utility) | Natural gas
Revenue from contracts with customers
Total operating revenues	4,386	4,302
Regulatory balancing accounts	225	87
Total operating revenues	4,611	4,389	$ 4,047
Pacific Gas & Electric Co (Utility) | Natural gas | Residential
Revenue from contracts with customers
Total operating revenues	2,517	2,325
Pacific Gas & Electric Co (Utility) | Natural gas | Commercial
Revenue from contracts with customers
Total operating revenues	597	605
Pacific Gas & Electric Co (Utility) | Natural gas | Transportation service only
Revenue from contracts with customers
Total operating revenues	1,211	1,249
Pacific Gas & Electric Co (Utility) | Natural gas | Other
Revenue from contracts with customers
Total operating revenues	$ 61	$ 123