Reportable Segments - Schedule of Financial Data (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Dec. 31, 2025
Segment Reporting Information [Line Items]
Revenues from external customers	$ 2,975	$ 2,920
Intersegment revenues	0	0
Utility natural gas, fuel and purchased power	970	1,006
Non-utility cost of revenues, including natural gas	1	1
Operation and maintenance expenses	766	747
Depreciation and amortization	423	363
Taxes other than income taxes	157	154
Interest expense and other finance charges	279	238
Income tax expense (benefit)	93	81
Interest income	(3)	(6)
Other expense (income), net	(27)	39
Net income (loss)	316	297
Interest income from securitization bonds	1	1
Expenditures for Long-lived Assets	1,174	1,340
Total Assets	47,837		$ 46,534
Natural Gas
Segment Reporting Information [Line Items]
Revenues from external customers	1,764	1,852
Corporate and Other
Segment Reporting Information [Line Items]
Revenues from external customers	2	2
Corporate and Other | Pension and Other Postretirement Plans Costs
Segment Reporting Information [Line Items]
Regulatory assets	377		383
Operating Segments
Segment Reporting Information [Line Items]
Revenues from external customers	2,975	2,920
Intersegment revenues	2	1
Utility natural gas, fuel and purchased power	971	1,007
Non-utility cost of revenues, including natural gas	1	1
Operation and maintenance expenses	767	747
Depreciation and amortization	423	363
Taxes other than income taxes	157	154
Interest expense and other finance charges	288	245
Income tax expense (benefit)	93	81
Interest income	(12)	(13)
Other expense (income), net	(27)	39
Net income (loss)	316	297
Operating Segments | Electric
Segment Reporting Information [Line Items]
Revenues from external customers	1,209	1,066
Intersegment revenues	0	0
Utility natural gas, fuel and purchased power	81	74
Non-utility cost of revenues, including natural gas	0	0
Operation and maintenance expenses	513	484
Depreciation and amortization	269	210
Taxes other than income taxes	85	78
Interest expense and other finance charges	131	101
Income tax expense (benefit)	16	25
Interest income	(4)	(4)
Other expense (income), net	(22)	(10)
Net income (loss)	140	108
Expenditures for Long-lived Assets	834	971
Total Assets	28,051		26,649
Operating Segments | Natural Gas
Segment Reporting Information [Line Items]
Revenues from external customers	1,764	1,852
Intersegment revenues	1	1
Utility natural gas, fuel and purchased power	890	933
Non-utility cost of revenues, including natural gas	1	1
Operation and maintenance expenses	258	265
Depreciation and amortization	148	147
Taxes other than income taxes	71	74
Interest expense and other finance charges	70	59
Income tax expense (benefit)	81	105
Interest income	0	(2)
Other expense (income), net	(4)	43
Net income (loss)	250	228
Expenditures for Long-lived Assets	332	363
Total Assets	18,399		18,405
Operating Segments | Corporate and Other
Segment Reporting Information [Line Items]
Revenues from external customers	2	2
Intersegment revenues	1	0
Utility natural gas, fuel and purchased power	0	0
Non-utility cost of revenues, including natural gas	0	0
Operation and maintenance expenses	(4)	(2)
Depreciation and amortization	6	6
Taxes other than income taxes	1	2
Interest expense and other finance charges	87	85
Income tax expense (benefit)	(4)	(49)
Interest income	(8)	(7)
Other expense (income), net	(1)	6
Net income (loss)	(74)	(39)
Expenditures for Long-lived Assets	8	6
Total Assets	1,387		$ 1,480
Eliminations
Segment Reporting Information [Line Items]
Revenues from external customers	0	0
Intersegment revenues	(2)	(1)
Utility natural gas, fuel and purchased power	(1)	(1)
Non-utility cost of revenues, including natural gas	0	0
Operation and maintenance expenses	(1)	0
Depreciation and amortization	0	0
Taxes other than income taxes	0	0
Interest expense and other finance charges	(9)	(7)
Income tax expense (benefit)	0	0
Interest income	9	7
Other expense (income), net	0	0
Net income (loss)	$ 0	$ 0