Income Taxes - Schedule of Accumulated Deferred Income Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disclosure Income Taxes Schedule Of Accumulated Deferred Income Tax Assets And Liabilities [Abstract]
Deferred State and Local Income Tax Expense (Benefit)	$ 100	$ 7,800	$ 8,200
Deferred income tax liabilities:
Property, plant and equipment	252,125	238,687
Acquisition adjustment	5,564	5,915
Deferred Tax Liabilities Loss On Reacquired Debt	145	164
Deferred Income Tax Liability - Deferred Gas Costs	3,550	11,288
Deferred Income Tax Liability, Natural Gas Conversion Costs	4,824	5,026
Deferred Income Tax Liability, Storm Reserve	5,797	5,791
Other	9,655	8,236
Total deferred income tax liabilities	281,660	275,107
Deferred income tax assets:
Pension and other employee benefits	4,993	3,985
Environmental costs	951	1,052
Net operating loss carryforwards	1,847	1,488
Storm reserve liability	213	453
Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals	3,335	9,007
Other	11,239	2,955
Total deferred income tax assets	22,578	18,940
Deferred Income Tax Liabilities, Net	$ 259,082	$ 256,167