CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025
CURRENT ASSETS
Cash and cash equivalents	$ 6,409	$ 6,604
Customer and other receivables	503,844	579,831
Accrued unbilled revenues (Note 4)	208,583	173,692
Allowance for doubtful accounts (Note 4)	(24,626)	(25,495)
Materials and supplies (at average cost)	543,198	546,329
Income tax receivable	8,416	5,979
Fossil fuel (at average cost)	19,955	18,824
Assets from risk management activities (Note 10)	388	3,250
Deferred fuel and purchased power regulatory asset (Note 7)	55,432	149,068
Other regulatory assets (Note 7)	141,297	136,941
Other current assets	151,984	108,686
Total current assets	1,614,880	1,703,709
INVESTMENTS AND OTHER ASSETS
Nuclear decommissioning trusts (Notes 14 and 15)	1,392,817	1,414,166
Other special use funds (Notes 14 and 15)	437,745	434,827
Assets from risk management activities (Note 10)	466	5,137
Other assets	159,288	144,997
Total investments and other assets	1,990,316	1,999,127
PROPERTY, PLANT AND EQUIPMENT
Plant in service and held for future use	27,616,435	27,370,296
Accumulated depreciation and amortization	(9,146,511)	(9,012,021)
Net	18,469,924	18,358,275
Construction work in progress	1,888,288	1,649,542
Palo Verde sale leaseback, net of accumulated depreciation (Note 9)	31,641	32,035
Intangible assets, net of accumulated amortization	539,939	575,978
Nuclear fuel, net of accumulated amortization	116,743	104,274
Total property, plant and equipment	21,046,535	20,720,104
DEFERRED DEBITS
Regulatory assets (Note 7)	1,454,210	1,463,357
Operating lease right-of-use assets (Note 17)	4,060,364	3,649,669
Assets for other postretirement benefits (Note 8)	411,088	399,334
Other	113,234	96,299
Total deferred debits	6,038,896	5,608,659
TOTAL ASSETS	30,690,627	30,031,599
CURRENT LIABILITIES
Accounts payable	601,648	680,203
Accrued taxes	240,006	186,605
Accrued interest	100,454	105,637
Common dividends payable	0	110,022
Short-term borrowings (Note 6)	594,100	757,005
Current maturities of long-term debt (Note 6)	600,000	600,000
Customer deposits	78,234	63,776
Liabilities from risk management activities (Note 10)	55,918	35,141
Liabilities for asset retirements	57,428	71,698
Operating lease liabilities (Note 17)	136,417	188,586
Regulatory liabilities (Note 7)	117,241	210,909
Other current liabilities	114,274	151,444
Total current liabilities	2,695,720	3,161,026
LONG-TERM DEBT LESS CURRENT MATURITIES (Note 6)	9,801,675	9,205,676
DEFERRED CREDITS AND OTHER
Liabilities from risk management activities (Note 10)	5,719	1,495
Deferred income taxes	2,479,565	2,470,932
Regulatory liabilities (Note 7)	1,751,277	1,736,121
Liabilities for pension benefits (Note 8)	170,295	167,636
Liabilities for asset retirements	1,229,369	1,198,601
Customer advances	618,106	632,169
Coal mine reclamation	161,686	159,587
Deferred investment tax credit	307,171	308,261
Unrecognized tax benefits	106,924	105,484
Operating lease liabilities (Note 17)	4,011,094	3,548,365
Other	241,058	249,171
Total deferred credits and other	11,082,264	10,577,822
COMMITMENTS AND CONTINGENCIES (Note 11)
EQUITY
Common stock, no par value; 300,000,000 shares authorized, 121,233,629 and 120,950,839 shares issued at respective dates	3,219,691	3,231,372
Treasury stock at cost; 46,968 and 46,968 shares at respective dates	(3,323)	(3,323)
Total common stock	3,216,368	3,228,049
Retained earnings	3,883,738	3,850,817
Accumulated other comprehensive loss (Note 16)	(31,949)	(32,408)
Total shareholder equity	7,068,157	7,046,458
Noncontrolling interests (Note 9)	42,811	40,617
Total equity	7,110,968	7,087,075
TOTAL LIABILITIES AND EQUITY	$ 30,690,627	$ 30,031,599