CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
CURRENT ASSETS
Cash and cash equivalents	$ 6,604	$ 3,838
Customer and other receivables	579,831	525,608
Accrued unbilled revenues (Note 4)	173,692	176,903
Allowance for doubtful accounts (Note 4)	(25,495)	(24,849)
Materials and supplies (at average cost)	546,329	469,022
Income tax receivable (Note 5)	5,979	0
Fossil fuel (at average cost)	18,824	32,420
Assets from risk management activities (Note 13)	3,250	10,578
Deferred fuel and purchased power regulatory asset (Note 8)	149,068	287,597
Other regulatory assets (Note 8)	136,941	133,372
Other current assets	108,686	74,915
Total current assets	1,703,709	1,689,404
INVESTMENTS AND OTHER ASSETS
Nuclear decommissioning trusts (Notes 17 and 18)	1,414,166	1,282,845
Other special use funds (Notes 17 and 18)	434,827	408,357
Assets from risk management activities (Note 13)	5,137	5,980
Other assets	144,997	115,095
Total investments and other assets	1,999,127	1,812,277
PROPERTY, PLANT AND EQUIPMENT (Notes 1, 7 and 11)
Plant in service and held for future use	27,370,296	25,860,950
Accumulated depreciation and amortization	(9,012,021)	(9,027,426)
Net	18,358,275	16,833,524
Construction work in progress	1,649,542	1,592,659
Palo Verde sale leaseback, net of accumulated depreciation of $110,886 and $268,894 (Note 12)	32,035	82,556
Intangible assets, net of accumulated amortization of $1,057,812 and $925,880	575,978	591,310
Nuclear fuel, net of accumulated amortization of $111,096 and $115,894	104,274	97,850
Total property, plant and equipment	20,720,104	19,197,899
DEFERRED DEBITS
Regulatory assets (Notes 1, 5, 8 and 9)	1,463,357	1,389,489
Operating lease right-of-use assets (Note 20)	3,649,669	1,605,463
Assets for other postretirement benefits (Note 9)	399,334	342,102
Other	96,299	66,126
Total deferred debits	5,608,659	3,403,180
TOTAL ASSETS	30,031,599	26,102,760
CURRENT LIABILITIES
Accounts payable	680,203	485,426
Accrued taxes	186,605	175,863
Accrued interest	105,637	81,799
Common dividends payable	110,022	106,592
Short-term borrowings (Note 6)	757,005	568,450
Current maturities of long-term debt (Note 6)	600,000	800,000
Customer deposits	63,776	44,345
Liabilities from risk management activities (Note 13)	35,141	52,340
Liabilities for asset retirements (Note 21)	71,698	50,009
Operating lease liabilities (Note 20)	188,586	100,367
Regulatory liabilities (Note 8)	210,909	206,955
Other current liabilities	151,444	171,651
Total current liabilities	3,161,026	2,843,797
LONG-TERM DEBT LESS CURRENT MATURITIES (Note 7)	9,205,676	8,058,648
DEFERRED CREDITS AND OTHER
Liabilities from risk management activities (Note 13)	1,495	9,446
Deferred income taxes (Note 5)	2,470,932	2,444,473
Regulatory liabilities (Notes 1, 5, 8 and 9)	1,736,121	1,855,278
Liabilities for pension benefits (Note 9)	167,636	139,317
Liabilities for asset retirements (Note 21)	1,198,601	1,096,577
Customer advances	632,169	569,343
Coal mine reclamation	159,587	171,483
Deferred investment tax credit	308,261	249,490
Unrecognized tax benefits	105,484	44,233
Operating lease liabilities (Note 20)	3,548,365	1,520,877
Other	249,171	242,320
Total deferred credits and other	10,577,822	8,342,837
COMMITMENTS AND CONTINGENCIES (Note 14)
EQUITY
Common stock, no par value; authorized 300,000,000 and 150,000,000 shares authorized at respective dates, 120,950,839 and 119,143,782 shares issued at respective dates	3,231,372	3,121,617
Treasury stock at cost; 46,968 and 46,968 shares at respective dates	(3,323)	(3,323)
Total common stock	3,228,049	3,118,294
Retained earnings	3,850,817	3,666,959
Accumulated other comprehensive loss (Note 19)	(32,408)	(30,942)
Total shareholder equity	7,046,458	6,754,311
Noncontrolling interests (Note 12)	40,617	103,167
Total equity	7,087,075	6,857,478
TOTAL LIABILITIES AND EQUITY	$ 30,031,599	$ 26,102,760