Regulatory Matters - Schedule of Regulatory Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
Detail of regulatory liabilities
Total regulatory liabilities	$ 2,062,233	$ 2,175,788
Less: current regulatory liabilities	206,955	209,923
Total non-current regulatory liabilities	1,855,278	1,965,865
Asset retirement obligations and removal costs
Detail of regulatory liabilities
Total regulatory liabilities	358,403	486,751
Other postretirement benefits
Detail of regulatory liabilities
Total regulatory liabilities	238,113	226,726
Four Corners coal reclamation
Detail of regulatory liabilities
Total regulatory liabilities	77,532	68,521
Renewable energy standard
Detail of regulatory liabilities
Total regulatory liabilities	68,523	60,667
Income taxes — deferred investment tax credit
Detail of regulatory liabilities
Total regulatory liabilities	66,327	55,917
Income taxes — change in rates
Detail of regulatory liabilities
Total regulatory liabilities	59,133	43,251
Spent nuclear fuel
Detail of regulatory liabilities
Total regulatory liabilities	26,818	33,154
Demand side management
Detail of regulatory liabilities
Total regulatory liabilities	23,927	14,374
Sundance maintenance
Detail of regulatory liabilities
Total regulatory liabilities	23,086	19,989
TCA Balancing Account
Detail of regulatory liabilities
Total regulatory liabilities	14,834	3,425
Property tax deferral
Detail of regulatory liabilities
Total regulatory liabilities	4,785	10,850
Tax expense adjustor mechanism
Detail of regulatory liabilities
Total regulatory liabilities	4,343	4,835
Other
Detail of regulatory liabilities
Total regulatory liabilities	113	2,317
ACC | Excess deferred income taxes - Tax Cuts and Jobs Act
Detail of regulatory liabilities
Total regulatory liabilities	888,896	930,344
FERC | Excess deferred income taxes - Tax Cuts and Jobs Act
Detail of regulatory liabilities
Total regulatory liabilities	$ 207,400	$ 214,667