Accounting For Income Taxes - Schedule of Deferred Income Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Deferred income tax assets:
Regulatory liabilities	$ 200,513	$ 179,871
Tax credits and NOL carryforwards	64,994	57,516
Provisions for pensions	25,650	37,501
Other	38,181	42,641
Total gross deferred income tax assets	329,338	317,529
Valuation allowances for deferred tax assets	(9,626)	(10,021)
Total deferred income tax assets after valuation allowances	319,712	307,508
Deferred income tax liabilities:
Utility property, plant, and equipment	688,856	666,639
Regulatory assets	264,978	232,697
Other	8,587	2,884
Total deferred income tax liabilities	962,421	902,220
Net long-term deferred income tax liability	$ 642,709	$ 594,712