Income Taxes - Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Deferred tax assets:
Advances and contributions	$ 25,714	$ 25,462
Unamortized investment tax credit	517	575
Pensions, postretirement benefits and stock-based compensation	17,844	23,161
Debt premium, net	4,157	4,868
California franchise tax	713	640
Deferred revenue	841	1,444
Tax related regulatory liability	24,358	25,750
Other	7,077	6,627
Total deferred tax assets	81,221	88,527
Deferred tax liabilities:
Utility plant	243,786	229,500
Pension and postretirement	13,247	17,709
Deferred gain and other-property	6,456	5,982
Regulatory asset - business combinations debt premium, net	4,157	4,868
Intangibles	2,693	2,943
Tax related regulatory asset	44,155	38,599
Section 481(a) adjustments	0	1,573
Other	5,255	5,508
Total deferred tax liabilities	319,749	306,682
Net deferred tax liabilities	$ 238,528	$ 218,155