Regulatory Matters - Schedule of Regulatory Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Detail of regulatory liabilities
Total regulatory liabilities	$ 2,175,788	$ 2,333,351
Regulatory liabilities (Note 3)	209,923	271,575
Total non-current regulatory liabilities	1,965,865	2,061,776
Asset retirement obligations
Detail of regulatory liabilities
Total regulatory liabilities	392,383	354,002
Other postretirement benefits
Detail of regulatory liabilities
Total regulatory liabilities	226,726	270,604
Removal costs
Detail of regulatory liabilities
Total regulatory liabilities	94,368	106,889
Deferred fuel and purchased power — mark-to-market (Note 16)
Detail of regulatory liabilities
Total regulatory liabilities	0	96,367
Income taxes — change in rates
Detail of regulatory liabilities
Total regulatory liabilities	60,667	64,806
Four Corners coal reclamation
Detail of regulatory liabilities
Total regulatory liabilities	55,917	52,592
Income taxes — deferred investment tax credit
Detail of regulatory liabilities
Total regulatory liabilities	68,521	48,035
Spent nuclear fuel
Detail of regulatory liabilities
Total regulatory liabilities	33,154	39,217
Renewable energy program
Detail of regulatory liabilities
Total regulatory liabilities	43,251	35,720
FERC transmission true up
Detail of regulatory liabilities
Total regulatory liabilities	1,869	22,895
Property tax deferral
Detail of regulatory liabilities
Total regulatory liabilities	10,850	15,521
Sundance maintenance
Detail of regulatory liabilities
Total regulatory liabilities	19,989	16,893
Demand side management
Detail of regulatory liabilities
Total regulatory liabilities	14,374	8,461
Tax expense adjustor mechanism
Detail of regulatory liabilities
Total regulatory liabilities	4,835	4,835
Other
Detail of regulatory liabilities
Total regulatory liabilities	3,873	3,092
ACC | Excess deferred income taxes - ACC - Tax Cuts and Jobs Act
Detail of regulatory liabilities
Total regulatory liabilities	930,344	971,545
FERC | Excess deferred income taxes - ACC - Tax Cuts and Jobs Act
Detail of regulatory liabilities
Total regulatory liabilities	$ 214,667	$ 221,877