Regulatory Matters - Regulatory Assets, Net (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Regulatory Assets [Line Items]
Regulatory assets, net not earning a return	$ 84,887	$ 119,236
Total regulatory assets, net	154,621	158,230
Less: current regulatory asset, net	2,629	1,748
Net regulatory assets, less current portion	$ 151,992	156,482
Minimum
Regulatory Assets [Line Items]
Estimated service lives of assets	5 years
Maximum
Regulatory Assets [Line Items]
Estimated service lives of assets	75 years
Income tax temporary differences
Regulatory Assets [Line Items]
Total regulatory assets, net	$ 22,420	6,230
Postretirement pensions and other medical benefits
Regulatory Assets [Line Items]
Total regulatory assets, net	62,197	94,362
Business combinations debt premium
Regulatory Assets [Line Items]
Total regulatory assets, net	19,937	22,479
Balancing and memorandum accounts, net
Regulatory Assets [Line Items]
Total regulatory assets, net	38,334	25,463
WRA
Regulatory Assets [Line Items]
Total regulatory assets, net	2,588	323
Other
Regulatory Assets [Line Items]
Total regulatory assets, net	$ 9,145	$ 9,373