CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
CURRENT ASSETS
Cash and cash equivalents	$ 3,838	$ 4,955
Customer and other receivables	525,608	513,892
Accrued unbilled revenues	176,903	167,553
Allowance for doubtful accounts (Note 2)	(24,849)	(22,433)
Materials and supplies (at average cost)	469,022	444,344
Income tax receivable (Note 4)	0	332
Fossil fuel (at average cost)	32,420	49,203
Assets from risk management activities (Note 15)	10,578	6,808
Assets held for sale (Note 20)	0	35,139
Deferred fuel and purchased power regulatory asset (Note 3)	287,597	463,195
Other regulatory assets (Note 3)	133,372	162,562
Other current assets	74,915	101,417
Total current assets	1,689,404	1,926,967
INVESTMENTS AND OTHER ASSETS
Nuclear decommissioning trusts (Notes 12 and 18)	1,282,845	1,201,246
Other special use funds (Notes 12, 17 and 18)	408,357	362,781
Assets from risk management activities (Note 15)	5,980	0
Other assets	115,095	102,845
Total investments and other assets	1,812,277	1,666,872
PROPERTY, PLANT AND EQUIPMENT (Notes 1, 6 and 9)
Plant in service and held for future use	25,860,950	24,211,167
Accumulated depreciation and amortization	(9,027,426)	(8,408,040)
Net	16,833,524	15,803,127
Construction work in progress	1,592,659	1,724,004
Palo Verde sale leaseback, net of accumulated depreciation of $268,894 and $264,624 (Note 17)	82,556	86,426
Intangible assets, net of accumulated amortization of $925,880 and $885,505	591,310	267,110
Nuclear fuel, net of accumulated amortization of $115,894 and $118,074	97,850	99,490
Total property, plant and equipment	19,197,899	17,980,157
DEFERRED DEBITS
Regulatory assets (Notes 1, 3, 4 and 7)	1,389,489	1,390,279
Operating lease right-of-use assets (Note 8)	1,605,463	1,309,975
Assets for pension and other postretirement benefits (Note 7)	342,102	323,438
Other	66,126	63,465
Total deferred debits	3,403,180	3,087,157
TOTAL ASSETS	26,102,760	24,661,153
CURRENT LIABILITIES
Accounts payable	485,426	442,455
Accrued taxes	175,863	166,833
Accrued interest	81,799	72,916
Common dividends payable	106,592	99,813
Short-term borrowings (Note 5)	568,450	609,500
Current maturities of long-term debt (Note 6)	800,000	875,000
Customer deposits	44,345	42,037
Liabilities from risk management activities (Note 15)	52,340	80,913
Liabilities for asset retirements (Note 11)	50,009	28,550
Operating lease liabilities (Note 8)	100,367	67,883
Regulatory liabilities (Note 3)	206,955	209,923
Other current liabilities	171,651	193,524
Total current liabilities	2,843,797	2,889,347
LONG-TERM DEBT LESS CURRENT MATURITIES (Note 6)	8,058,648	7,540,622
DEFERRED CREDITS AND OTHER
Deferred income taxes (Note 4)	2,444,473	2,416,480
Regulatory liabilities (Notes 1, 3, 4 and 7)	1,855,278	1,965,865
Liabilities for asset retirements (Note 11)	1,096,577	937,451
Liabilities for pension benefits (Note 7)	139,317	112,702
Liabilities from risk management activities (Note 15)	9,446	42,975
Customer advances	569,343	533,580
Coal mine reclamation	171,483	184,007
Deferred investment tax credit	249,490	257,743
Unrecognized tax benefits (Note 4)	44,233	33,861
Operating lease liabilities (Note 8)	1,520,877	1,210,189
Other	242,320	251,469
Total deferred credits and other	8,342,837	7,946,322
COMMITMENTS AND CONTINGENCIES (Note 10)
EQUITY
Common stock, no par value; authorized 150,000,000 shares, 119,143,782 and 113,537,689 issued at respective dates	3,121,617	2,752,676
Treasury stock at cost; 46,968 and 113,272 shares at respective dates	(3,323)	(8,185)
Total common stock	3,118,294	2,744,491
Retained earnings	3,666,959	3,466,317
Accumulated other comprehensive loss (Note 19)	(30,942)	(33,144)
Total shareholders’ equity	6,754,311	6,177,664
Noncontrolling interests (Note 17)	103,167	107,198
Total equity	6,857,478	6,284,862
TOTAL LIABILITIES AND EQUITY	$ 26,102,760	$ 24,661,153