Regulatory Matters - Schedule of Regulatory Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Detail of regulatory assets
Regulatory assets, current	$ 518,524	$ 291,713
Regulatory assets, non-current	1,192,987	1,133,987
Pension
Detail of regulatory assets
Regulatory assets, current	0	0
Regulatory assets, non-current	509,751	469,953
Deferred fuel and purchased power
Detail of regulatory assets
Regulatory assets, current	388,148	175,835
Regulatory assets, non-current	0	0
Income taxes — AFUDC equity
Detail of regulatory assets
Regulatory assets, current	7,625	7,169
Regulatory assets, non-current	164,768	158,776
Ocotillo deferral
Detail of regulatory assets
Regulatory assets, current	9,507	0
Regulatory assets, non-current	138,143	95,723
Retired power plant costs
Detail of regulatory assets
Regulatory assets, current	15,160	28,181
Regulatory assets, non-current	99,681	114,214
SCR deferral
Detail of regulatory assets
Regulatory assets, current	8,147	0
Regulatory assets, non-current	97,624	81,307
Lost fixed cost recovery
Detail of regulatory assets
Regulatory assets, current	63,889	41,807
Regulatory assets, non-current	0	0
Deferred property taxes
Detail of regulatory assets
Regulatory assets, current	8,569	8,569
Regulatory assets, non-current	41,057	49,626
Deferred compensation
Detail of regulatory assets
Regulatory assets, current	0	0
Regulatory assets, non-current	33,997	36,195
Income taxes — investment tax credit basis adjustment
Detail of regulatory assets
Regulatory assets, current	1,129	1,113
Regulatory assets, non-current	23,639	24,291
Four Corners cost deferral
Detail of regulatory assets
Regulatory assets, current	8,077	8,077
Regulatory assets, non-current	15,998	24,075
Palo Verde VIE
Detail of regulatory assets
Regulatory assets, current	0	0
Regulatory assets, non-current	21,094	21,255
Coal reclamation
Detail of regulatory assets
Regulatory assets, current	2,978	1,068
Regulatory assets, non-current	13,862	16,999
Loss on reacquired debt
Detail of regulatory assets
Regulatory assets, current	1,648	1,689
Regulatory assets, non-current	9,372	10,877
Mead-Phoenix transmission line — contributions in aid of construction
Detail of regulatory assets
Regulatory assets, current	332	332
Regulatory assets, non-current	9,048	9,380
Tax expense adjustor mechanism
Detail of regulatory assets
Regulatory assets, current	656	6,226
Regulatory assets, non-current	5,845	0
TCA balancing account
Detail of regulatory assets
Regulatory assets, current	170	0
Regulatory assets, non-current	3,663	0
Tax expense of Medicare subsidy
Detail of regulatory assets
Regulatory assets, current	1,235	1,235
Regulatory assets, non-current	2,469	3,704
Demand side management
Detail of regulatory assets
Regulatory assets, current	919	0
Regulatory assets, non-current	0	7,268
PSA interest
Detail of regulatory assets
Regulatory assets, current	335	4,355
Regulatory assets, non-current	0	0
Deferred fuel and purchased power - mark-to-market
Detail of regulatory assets
Regulatory assets, current	0	3,341
Regulatory assets, non-current	0	9,244
Other
Detail of regulatory assets
Regulatory assets, current	0	2,716
Regulatory assets, non-current	$ 2,976	$ 1,100