Income Taxes (Tables)

6 Months Ended

Jun. 30, 2025

Income Tax Disclosure [Abstract]

Summary of Significant Factors Impact on Difference Between Effective Tax Rate and Federal Statutory Rate

The following table summarizes the significant factors impacting the difference between the Company's effective tax rate and the federal statutory rate for the three and six months ended June 30 (dollars in millions):

	Three months ended June 30,										Six months ended June 30,
	2025					2024					2025					2024
Federal income taxes at statutory rates	$	3		21.0	%	$	5		21.0	%	$	22		21.0	%	$	20		21.0	%
Increase (decrease) in tax resulting from:
Flow through related to deduction of meters      and mixed service costs (1)		(1	)	(7.1	)		(3	)	(12.6	)		(4	)	(3.8	)		(12	)	(12.3	)
Tax effect of regulatory treatment of utility       plant differences		(1	)	(7.2	)		(1	)	(6.3	)		(6	)	(5.8	)		(6	)	(6.5	)
State income tax expense		—		—			—		—			1		0.9			1		0.7
Total income tax expense	$	1		6.7	%	$	1		2.1	%	$	13		12.3	%	$	3		2.9	%

(1)The Company's general rate cases included approval of base rate increases, offset by tax customer credits. As the tax customer credits are returned to customers, this results in a decrease to income tax expense as a result of flowing through the benefits related to meters and mixed service costs.