Income Taxes (Tables)

3 Months Ended

Mar. 31, 2023

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 months ended March 31 (dollars in thousands):

	2023					2022
Federal income taxes at statutory rates	$	10,126		21.0	%	$	12,753		21.0	%
Increase (decrease) in tax resulting from:
Flow through related to deduction of meters      and mixed service costs (1)		(13,523	)	(28.0	)		(17,434	)	(28.7	)
Tax effect of regulatory treatment of utility       plant differences (2)		(3,687	)	(7.7	)		(6,322	)	(10.4	)
State income tax expense		566		1.2			823		1.4
Settlement of equity awards		—		—			(19	)	—
Other		(110	)	(0.2	)		(637	)	(1.1	)
Total income tax benefit	$	(6,628	)	(13.7	)%	$	(10,836	)	(17.8	)%

(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. The decrease in income tax expense offsets the increases in base rate granted to the Company in these general rate cases.

(2)Prior to 2022, for depreciation-related temporary differences under the normalization tax accounting method, the Company utilized the average rate assumption method to compute the amounts returned to customers. Beginning in 2022, the Company changed to the alternative method, to be in compliance with recently released revenue procedures and private letter rulings.