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Segment Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
Segment Information (Details) - USD ($) $ in Millions	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Segment Reporting [Abstract]
Equity Method Investments	$ 204		$ 204		$ 165
Segment Reporting Information [Line Items]
Electric	3,176	$ 2,941	8,643	$ 7,430
Net income	609	603	1,282	1,185
Natural gas	268	219	1,364	1,082
Other	23	22	69	67
Regulated and Unregulated Operating Revenue	3,467	3,182	10,076	8,579
Equity Method Investments	204		204		165
Operating Segments
Segment Reporting Information [Line Items]
Regulated and Unregulated Operating Revenue	3,468	3,183	10,079	8,581
Intersegment Eliminations
Segment Reporting Information [Line Items]
Regulated and Unregulated Operating Revenue	(1)	(1)	(3)	(2)
Regulated Electric
Segment Reporting Information [Line Items]
Net income	629	632	1,202	1,148
Revenues Including Intersegment Revenues	3,176	2,942	8,644	7,431
Regulated Electric \| Operating Segments
Segment Reporting Information [Line Items]
Electric	3,176	2,941	8,643	7,430
Regulated Electric \| Intersegment Eliminations
Segment Reporting Information [Line Items]
Electric	0	1	1	1
Regulated Natural Gas
Segment Reporting [Abstract]
Equity Method Investments	204		204		165
Segment Reporting Information [Line Items]
Net income	10	0	161	111
Revenues Including Intersegment Revenues	269	219	1,366	1,083
Equity Method Investments	204		204		$ 165
Regulated Natural Gas \| Operating Segments
Segment Reporting Information [Line Items]
Natural gas	268	219	1,364	1,082
Regulated Natural Gas \| Intersegment Eliminations
Segment Reporting Information [Line Items]
Natural gas	1	0	2	1
All Other
Segment Reporting Information [Line Items]
Net income	(30)	(29)	(81)	(74)
All Other \| Operating Segments
Segment Reporting Information [Line Items]
Other	$ 23	$ 22	$ 69	$ 67