Significant Accounting Policies - Schedule of Property, Plant and Equipment (Detail) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Property Plant And Equipment [Line Items]
Total cost	$ 12,820	$ 12,520
Less accumulated depreciation	(3,348)	(3,443)
Construction work in progress	1,631	1,151
Total property, plant and equipment, net	11,103	10,228
PGS [Member]
Property Plant And Equipment [Line Items]
Total property, plant and equipment, net			$ 2,251
Electric Generation [Member]
Property Plant And Equipment [Line Items]
Total cost	6,574	6,732
General Plant and Other [Member]
Property Plant And Equipment [Line Items]
Total cost	$ 1,081	997
Minimum [Member] | Electric Generation [Member]
Property Plant And Equipment [Line Items]
Estimated useful lives	10 years
Minimum [Member] | General Plant and Other [Member]
Property Plant And Equipment [Line Items]
Estimated useful lives	4 years
Maximum [Member] | Electric Generation [Member]
Property Plant And Equipment [Line Items]
Estimated useful lives	60 years
Maximum [Member] | General Plant and Other [Member]
Property Plant And Equipment [Line Items]
Estimated useful lives	60 years
Electric Transmission [Member]
Property Plant And Equipment [Line Items]
Total cost	$ 1,245	1,182
Electric Transmission [Member] | Minimum [Member]
Property Plant And Equipment [Line Items]
Estimated useful lives	10 years
Electric Transmission [Member] | Maximum [Member]
Property Plant And Equipment [Line Items]
Estimated useful lives	75 years
Electric Distribution [Member]
Property Plant And Equipment [Line Items]
Total cost	$ 3,920	$ 3,609
Electric Distribution [Member] | Minimum [Member]
Property Plant And Equipment [Line Items]
Estimated useful lives	10 years
Electric Distribution [Member] | Maximum [Member]
Property Plant And Equipment [Line Items]
Estimated useful lives	60 years