Segment Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025		Mar. 31, 2024
Segment Reporting Information [Line Items]
Net Income (Loss)	$ 42		$ 43
Natural gas	68		54
Regulated and Unregulated Operating Revenue	327		310
Cost of natural sold and transported	33		24
Operating and maintenance expenses	63		56
Utilities Operating Expense, Depreciation and Amortization	49		45
Interest and Debt Expense	16		13
Income Tax Expense (Benefit)	12		13
Regulated Operating Revenue, Electric, Affiliate	56		53
Total revenues
Segment Reporting Information [Line Items]
Net Income (Loss)	42		43
Regulated Operating Revenue	327	[1]	310	[2]
Electric Fuel and Purchased Power	106		107
Cost of natural sold and transported	33		24
Operating and maintenance expenses	63		56
Utilities Operating Expense, Depreciation and Amortization	49		45
Segment Reporting, Other Segment Item, Amount	6		9
Interest and Debt Expense	16		13
Income Tax Expense (Benefit)	12		13
All Other
Segment Reporting Information [Line Items]
Net Income (Loss)	0		0
Regulated Electric Segment | Total revenues
Segment Reporting Information [Line Items]
Regulated Operating Revenue, Electric	259	[1]	256	[2]
Net Income (Loss)	29		33
Electric Fuel and Purchased Power	106		107
Cost of natural sold and transported	0		0
Operating and maintenance expenses	55		49
Utilities Operating Expense, Depreciation and Amortization	41		38
Segment Reporting, Other Segment Item, Amount	6		7
Interest and Debt Expense	14		12
Income Tax Expense (Benefit)	8		10
Regulated Natural Gas Segment | Total revenues
Segment Reporting Information [Line Items]
Net Income (Loss)	13		10
Natural gas	68	[1]	54	[2]
Electric Fuel and Purchased Power	0		0
Cost of natural sold and transported	33		24
Operating and maintenance expenses	8		7
Utilities Operating Expense, Depreciation and Amortization	8		7
Segment Reporting, Other Segment Item, Amount	0		2
Interest and Debt Expense	2		1
Income Tax Expense (Benefit)	$ 4		$ 3

[1] Operating revenues include $56 million of affiliate electric revenue.

[2] Operating revenues include $53 million of affiliate electric revenue.