CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2025	Dec. 31, 2024
CURRENT ASSETS
Cash and cash equivalents	$ 18,841	$ 3,838
Customer and other receivables	569,656	525,608
Accrued unbilled revenues (Note 4)	272,327	176,903
Allowance for doubtful accounts (Note 4)	(17,449)	(24,849)
Materials and supplies (at average cost)	509,269	469,022
Fossil fuel (at average cost)	17,670	32,420
Assets from risk management activities (Note 9)	10,903	10,578
Deferred fuel and purchased power regulatory asset (Note 6)	182,412	287,597
Other regulatory assets (Note 6)	121,436	133,372
Other current assets	102,843	74,915
Total current assets	1,787,908	1,689,404
INVESTMENTS AND OTHER ASSETS
Nuclear decommissioning trusts (Notes 13 and 14)	1,337,858	1,282,845
Other special use funds (Notes 13 and 14)	423,332	408,357
Assets from risk management activities (Note 9)	34,203	5,980
Other assets	140,619	115,095
Total investments and other assets	1,936,012	1,812,277
PROPERTY, PLANT AND EQUIPMENT
Plant in service and held for future use	25,895,037	25,860,950
Accumulated depreciation and amortization	(8,690,747)	(9,027,426)
Net	17,204,290	16,833,524
Construction work in progress	2,087,779	1,592,659
Palo Verde sale leaseback, net of accumulated depreciation (Note 8)	80,622	82,556
Intangible assets, net of accumulated amortization	569,047	591,310
Nuclear fuel, net of accumulated amortization	120,267	97,850
Total property, plant and equipment	20,062,005	19,197,899
DEFERRED DEBITS
Regulatory assets (Note 6)	1,357,382	1,389,489
Operating lease right-of-use assets (Note 16)	3,638,906	1,605,463
Assets for pension and other postretirement benefits (Note 7)	364,229	342,102
Other	88,739	66,126
Total deferred debits	5,449,256	3,403,180
TOTAL ASSETS	29,235,181	26,102,760
CURRENT LIABILITIES
Accounts payable	668,664	485,426
Accrued taxes	205,460	175,863
Accrued interest	84,760	81,799
Common dividends payable	106,869	106,592
Short-term borrowings (Note 5)	1,405,000	568,450
Current maturities of long-term debt (Note 5)	350,000	800,000
Customer deposits	53,272	44,345
Liabilities from risk management activities (Note 9)	25,692	52,340
Liabilities for asset retirements	41,226	50,009
Operating lease liabilities (Note 16)	191,628	100,367
Regulatory liabilities (Note 6)	182,458	206,955
Other current liabilities	112,213	171,651
Total current liabilities	3,427,242	2,843,797
LONG-TERM DEBT LESS CURRENT MATURITIES (Note 5)	8,507,002	8,058,648
DEFERRED CREDITS AND OTHER
Deferred income taxes	2,465,821	2,444,473
Regulatory liabilities (Note 6)	1,912,279	1,855,278
Liabilities for asset retirements	1,123,521	1,096,577
Liabilities for pension benefits (Note 7)	147,929	139,317
Liabilities from risk management activities (Note 9)	7,144	9,446
Customer advances	580,656	569,343
Coal mine reclamation	155,600	171,483
Deferred investment tax credit	246,189	249,490
Unrecognized tax benefits	45,815	44,233
Operating lease liabilities (Note 16)	3,550,894	1,520,877
Other	237,149	242,320
Total deferred credits and other	10,472,997	8,342,837
COMMITMENTS AND CONTINGENCIES (Note 10)
EQUITY
Common stock, no par value; 300,000,000 and 150,000,000 shares authorized at respective dates, 119,472,939 and 119,143,782 shares issued at respective dates	3,119,404	3,121,617
Treasury stock at cost; 46,968 and 46,968 shares at respective dates	(3,323)	(3,323)
Total common stock	3,116,081	3,118,294
Retained earnings	3,641,148	3,666,959
Accumulated other comprehensive loss (Note 15)	(30,441)	(30,942)
Total shareholder equity	6,726,788	6,754,311
Noncontrolling interests (Note 8)	101,152	103,167
Total equity	6,827,940	6,857,478
TOTAL LIABILITIES AND EQUITY	$ 29,235,181	$ 26,102,760