Regulatory Matters - Schedule of Regulatory Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Detail of regulatory liabilities
Total regulatory liabilities	$ 2,053,277	$ 2,175,788
Less: current regulatory liabilities	243,714	209,923
Total non-current regulatory liabilities	1,809,563	1,965,865
Asset retirement obligations
Detail of regulatory liabilities
Total regulatory liabilities	328,253	392,383
Other postretirement benefits
Detail of regulatory liabilities
Total regulatory liabilities	193,583	226,726
Removal costs
Detail of regulatory liabilities
Total regulatory liabilities	87,694	94,368
Income taxes — deferred investment tax credit
Detail of regulatory liabilities
Total regulatory liabilities	65,779	68,521
Four Corners coal reclamation
Detail of regulatory liabilities
Total regulatory liabilities	59,500	55,917
Renewable energy standard
Detail of regulatory liabilities
Total regulatory liabilities	59,344	43,251
Income taxes — change in rates
Detail of regulatory liabilities
Total regulatory liabilities	57,791	60,667
Demand side management
Detail of regulatory liabilities
Total regulatory liabilities	32,705	14,374
Spent nuclear fuel
Detail of regulatory liabilities
Total regulatory liabilities	28,431	33,154
Sundance maintenance
Detail of regulatory liabilities
Total regulatory liabilities	22,312	19,989
TCA Balancing Account
Detail of regulatory liabilities
Total regulatory liabilities	11,514	3,425
Property tax deferral
Detail of regulatory liabilities
Total regulatory liabilities	6,111	10,850
Tax expense adjustor mechanism
Detail of regulatory liabilities
Total regulatory liabilities	4,494	4,835
Other
Detail of regulatory liabilities
Total regulatory liabilities	111	2,317
ACC | Excess deferred income taxes - Tax Act
Detail of regulatory liabilities
Total regulatory liabilities	888,345	930,344
FERC | Excess deferred income taxes - Tax Act
Detail of regulatory liabilities
Total regulatory liabilities	$ 207,310	$ 214,667