Revenue Recognition (Disaggregation of Revenue) (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2022	Mar. 31, 2021
Operating revenue from contracts with customers		$ 0	$ 0
Total Operating Revenues	[1]	849	744
Electric Operations
Operating revenue from contracts with customers		647	571
Other revenues		8	8
Total Operating Revenues		655	579
Gas Distribution
Operating revenue from contracts with customers		194	164
Other revenues		0	1
Total Operating Revenues		194	165
Residential | Electric Operations
Operating revenue from contracts with customers		300	275
Residential | Gas Distribution
Operating revenue from contracts with customers		109	98
Commercial | Electric Operations
Operating revenue from contracts with customers		201	175
Commercial | Gas Distribution
Operating revenue from contracts with customers		48	39
Industrial | Electric Operations
Operating revenue from contracts with customers		108	88
Industrial | Gas Distribution
Operating revenue from contracts with customers		31	22
Other | Electric Operations
Operating revenue from contracts with customers		38	33
Other | Gas Distribution
Operating revenue from contracts with customers		$ 6	$ 5

[1] See Note 12 for amounts attributable to affiliates.