Regulatory Matters - Schedule of Regulatory Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Detail of regulatory liabilities
Total regulatory liabilities	$ 2,187,672	$ 2,175,788
Less: current regulatory liabilities	221,552	209,923
Total non-current regulatory liabilities	1,966,120	1,965,865
Asset retirement obligations
Detail of regulatory liabilities
Total regulatory liabilities	411,393	392,383
Other postretirement benefits
Detail of regulatory liabilities
Total regulatory liabilities	215,298	226,726
Removal costs
Detail of regulatory liabilities
Total regulatory liabilities	90,082	94,368
Income taxes — deferred investment tax credit
Detail of regulatory liabilities
Total regulatory liabilities	68,442	68,521
Income taxes — change in rates
Detail of regulatory liabilities
Total regulatory liabilities	60,589	60,667
Four Corners coal reclamation
Detail of regulatory liabilities
Total regulatory liabilities	56,557	55,917
Renewable energy standard
Detail of regulatory liabilities
Total regulatory liabilities	51,001	43,251
Spent nuclear fuel
Detail of regulatory liabilities
Total regulatory liabilities	31,552	33,154
Demand side management
Detail of regulatory liabilities
Total regulatory liabilities	20,905	14,374
Sundance maintenance
Detail of regulatory liabilities
Total regulatory liabilities	20,763	19,989
Property tax deferral
Detail of regulatory liabilities
Total regulatory liabilities	9,541	10,850
Tax expense adjustor mechanism
Detail of regulatory liabilities
Total regulatory liabilities	4,796	4,835
FERC Transmission true up
Detail of regulatory liabilities
Total regulatory liabilities	0	1,869
Other
Detail of regulatory liabilities
Total regulatory liabilities	3,090	3,873
ACC | Excess deferred income taxes - Tax Act
Detail of regulatory liabilities
Total regulatory liabilities	929,197	930,344
FERC | Excess deferred income taxes - Tax Act
Detail of regulatory liabilities
Total regulatory liabilities	$ 214,466	$ 214,667