Income Taxes - Federal Statutory Rate Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Income before income taxes	$ 90,943	$ 82,324	$ 68,847
Income Tax Statutory Rate Reconciliation [Abstract]
Income tax at federal statutory rate	19,098	17,288	14,458
Increase (decrease) in taxes attributable to:
State taxes, net of federal income tax benefit	6,001	5,328	4,572
Uncertain tax positions	(4,330)	1,483	1,678
Property flow-through	(9,045)	(13,091)	(8,573)
Reversal of excess deferred taxes recognized in regulatory liability	(3,625)	(3,885)	(3,295)
Pension flow-through	(597)	27	429
Stock-based compensation	(491)	(297)	(331)
Other items, net	(1,055)	1,643	(569)
Income tax expense	$ 5,956	$ 8,496	$ 8,369