Income Taxes - Schedule of Accumulated Deferred Income Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Disclosure Income Taxes Schedule Of Accumulated Deferred Income Tax Assets And Liabilities [Abstract]
Deferred State and Local Income Tax Expense (Benefit)	$ 7,800	$ 8,200	$ 4,900
Deferred income tax liabilities:
Property, plant and equipment	238,687	224,034
Acquisition adjustment	5,915	6,266
Deferred Tax Liabilities Loss On Reacquired Debt	164	183
Deferred Income Tax Liability - Deferred Gas Costs	11,288	2,366
Deferred Income Tax Liability, Natural Gas Conversion Costs	5,026	5,529
Deferred Income Tax Liability, Storm Reserve	5,791	5,783
Other	8,236	6,301
Total deferred income tax liabilities	275,107	250,462
Deferred income tax assets:
Pension and other employee benefits	3,985	5,354
Environmental costs	1,052	996
Net operating loss carryforwards	1,488	1,490
Storm reserve liability	453	448
Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals	9,007	4,843
Other	2,955	3,781
Total deferred income tax assets	18,940	16,912
Deferred income taxes	$ 256,167	$ 233,550