Segments and Related Information (Details) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Segment Reporting Information [Line Items]
Natural gas										$ 623	$ 493	$ 571
Other										39	37	35
Total operating revenues		$ 1,283	$ 1,388	$ 1,180	$ 1,250	$ 1,283	$ 1,388	$ 1,180	$ 1,250	5,756	5,101	5,112
Depreciation and amortization										926	825	791
Total interest charges and financing costs										258	238	221
Income tax (benefit) expense										(48)	(6)	47
Net income (loss)		$ 121	$ 246	$ 117	$ 107	$ 121	$ 246	$ 117	$ 107	606	591	543
Related Party Transaction - Electric Domestic Regulated Revenue										501	440	457
Related Party Transaction - Gas Domestic Regulated Revenue										1	1	1
Regulated Electricity
Segment Reporting Information [Line Items]
Revenues Including Intersegment Revenues										5,095	4,572	4,507
Depreciation and amortization										869	773	742
Total interest charges and financing costs										240	221	205
Income tax (benefit) expense										(53)	(14)	36
Net income (loss)										566	553	491
Regulated Natural Gas
Segment Reporting Information [Line Items]
Revenues Including Intersegment Revenues										624	493	572
Depreciation and amortization										56	51	49
Total interest charges and financing costs										18	17	16
Income tax (benefit) expense										6	7	12
Net income (loss)										29	30	40
All Other
Segment Reporting Information [Line Items]
Depreciation and amortization										1	1	0
Income tax (benefit) expense										(1)	1	(1)
Net income (loss)										11	8	12
Total revenues
Segment Reporting Information [Line Items]
Total operating revenues	[1],[2]									5,758	5,102	5,114
Total revenues | Regulated Electricity
Segment Reporting Information [Line Items]
Operating revenue, Regulated Electric	[2]									5,094	4,571	4,506
Total revenues | Regulated Natural Gas
Segment Reporting Information [Line Items]
Natural gas	[1]									623	493	571
Total revenues | All Other
Segment Reporting Information [Line Items]
Other										39	37	35
Intersegment Eliminations
Segment Reporting Information [Line Items]
Total operating revenues										(2)	(1)	(2)
Intersegment Eliminations | Regulated Electricity
Segment Reporting Information [Line Items]
Operating revenue, Regulated Electric										1	1	1
Intersegment Eliminations | Regulated Natural Gas
Segment Reporting Information [Line Items]
Natural gas										$ 1	$ 0	$ 1

[1] Operating revenues include $1 million of affiliate gas revenue for the years ended Dec. 31, 2021, 2020 and 2019, respectively. See Note 13 for further information.

[2] Operating revenues include $501 million, $440 million and $457 million of affiliate electric revenue for the years ended Dec. 31, 2021, 2020 and 2019, respectively. See Note 13 for further information.