SEGMENT AND RELATED INFORMATION - Electric Utilities' Revenues (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Revenue from External Customer [Line Items]
Total operating revenues	$ 23,113	$ 20,375	$ 21,419
Other electric revenues
Revenue from External Customer [Line Items]
Total operating revenues	718	672	636
Electric Utilities
Revenue from External Customer [Line Items]
Total operating revenues	18,300	16,497	17,095
Electric Utilities | Retail electric revenues
Revenue from External Customer [Line Items]
Total operating revenues	14,852	13,643	14,084
Electric Utilities | Wholesale electric revenues
Revenue from External Customer [Line Items]
Total operating revenues	2,455	1,945	2,152
Electric Utilities | Other electric revenues
Revenue from External Customer [Line Items]
Total operating revenues	$ 993	$ 909	$ 859