Regulatory Matters - Schedule of Regulatory Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
Detail of regulatory liabilities
Total regulatory liabilities	$ 1,947,030	$ 2,062,233
Less: current regulatory liabilities	210,909	206,955
Total non-current regulatory liabilities	1,736,121	1,855,278
AROs and removal costs
Detail of regulatory liabilities
Total regulatory liabilities	286,907	358,403
Other postretirement benefits
Detail of regulatory liabilities
Total regulatory liabilities	233,952	238,113
Four Corners coal reclamation
Detail of regulatory liabilities
Total regulatory liabilities	97,988	77,532
Income taxes — deferred investment tax credit
Detail of regulatory liabilities
Total regulatory liabilities	81,949	66,327
Income taxes — change in rates
Detail of regulatory liabilities
Total regulatory liabilities	56,260	59,133
RES
Detail of regulatory liabilities
Total regulatory liabilities	54,551	68,523
DSM
Detail of regulatory liabilities
Total regulatory liabilities	26,228	23,927
Sundance maintenance
Detail of regulatory liabilities
Total regulatory liabilities	25,668	23,086
Spent nuclear fuel
Detail of regulatory liabilities
Total regulatory liabilities	20,492	26,818
TCA Balancing Account
Detail of regulatory liabilities
Total regulatory liabilities	4,860	14,834
TEAM
Detail of regulatory liabilities
Total regulatory liabilities	3,738	4,343
Deferred fuel and purchased power — mark-to-market (Note 13)
Detail of regulatory liabilities
Total regulatory liabilities	3,641	0
Other
Detail of regulatory liabilities
Total regulatory liabilities	3,063	4,898
ACC | Excess deferred income taxes - Tax Cuts and Jobs Act
Detail of regulatory liabilities
Total regulatory liabilities	847,572	888,896
FERC | Excess deferred income taxes - Tax Cuts and Jobs Act
Detail of regulatory liabilities
Total regulatory liabilities	$ 200,161	$ 207,400