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Segment Information (Details) - USD ($) $ in Millions	3 Months Ended
Segment Information (Details) - USD ($) $ in Millions	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Segment Reporting Information [Line Items]
Equity investments in unconsolidated subsidiaries	$ 158		$ 155
Regulated Operating Revenue, Electric	2,203	$ 2,325
Net income	295	315
Regulated Operating Revenue, Gas	583	794
Unregulated Operating Revenue	25	22
Regulated and Unregulated Operating Revenue	2,811	3,141
Electricity, US Regulated [Member]
Segment Reporting Information [Line Items]
Net income	227	234
Natural Gas, US Regulated [Member]
Segment Reporting Information [Line Items]
Equity investments in unconsolidated subsidiaries	158		$ 155
Net income	91	105
Revenues Including Intersegment Revenues	583	795
All Other
Segment Reporting Information [Line Items]
Net income	(23)	(24)
Operating Segments
Segment Reporting Information [Line Items]
Regulated and Unregulated Operating Revenue	2,811	3,142
Operating Segments \| Electricity, US Regulated [Member]
Segment Reporting Information [Line Items]
Regulated Operating Revenue, Electric	2,203	2,325
Operating Segments \| Natural Gas, US Regulated [Member]
Segment Reporting Information [Line Items]
Regulated Operating Revenue, Gas	583	794
Operating Segments \| All Other
Segment Reporting Information [Line Items]
Unregulated Operating Revenue	25	22
Intersegment Eliminations
Segment Reporting Information [Line Items]
Regulated and Unregulated Operating Revenue	0	(1)
Intersegment Eliminations \| Natural Gas, US Regulated [Member]
Segment Reporting Information [Line Items]
Regulated Operating Revenue, Gas	$ 0	$ 1