CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
CURRENT ASSETS
Cash and cash equivalents	$ 15,108	$ 4,832
Customer and other receivables	664,936	453,209
Accrued unbilled revenues	226,998	164,764
Allowance for doubtful accounts (Note 2)	(20,648)	(23,778)
Materials and supplies (at average cost)	443,852	410,481
Income tax receivable	0	14,086
Fossil fuel (at average cost)	49,977	40,155
Assets from risk management activities (Note 7)	11,376	87,835
Asset, Held-for-Sale, Not Part of Disposal Group, Current	31,706	0
Deferred fuel and purchased power regulatory asset (Note 4)	526,666	460,561
Other regulatory assets (Note 4)	103,653	78,318
Other current assets	108,314	60,091
Total current assets	2,161,938	1,750,554
INVESTMENTS AND OTHER ASSETS
Nuclear decommissioning trusts (Notes 11 and 12)	1,120,463	1,073,410
Other special use funds (Notes 11 and 12)	368,159	347,231
Assets from risk management activities (Note 7)	3,171	44,394
Other assets	102,863	125,672
Total investments and other assets	1,594,656	1,590,707
PROPERTY, PLANT AND EQUIPMENT
Plant in service and held for future use	23,939,969	22,452,146
Accumulated depreciation and amortization	(8,319,351)	(7,929,878)
Net	15,620,618	14,522,268
Construction work in progress	1,536,323	1,882,791
Palo Verde sale leaseback, net of accumulated depreciation (Note 6)	87,394	90,296
Intangible assets, net of accumulated amortization	249,480	258,880
Nuclear fuel, net of accumulated amortization	112,956	100,119
Total property, plant and equipment	17,606,771	16,854,354
DEFERRED DEBITS
Regulatory assets (Note 4)	1,303,244	1,283,221
Operating lease right-of-use assets (Note 14)	1,307,643	801,688
Assets for pension and other postretirement benefits (Note 5)	407,065	396,599
Other	53,109	46,282
Total deferred debits	3,071,061	2,527,790
TOTAL ASSETS	24,434,426	22,723,405
CURRENT LIABILITIES
Accounts payable	404,971	430,425
Accrued taxes	265,463	164,440
Accrued interest	76,192	61,217
Common dividends payable	0	97,895
Short-term borrowings (Note 3)	424,000	340,720
Current maturities of long-term debt (Note 3)	250,000	50,685
Customer deposits	40,557	41,769
Liabilities from risk management activities (Note 7)	42,732	37,697
Liabilities for asset retirements (Note 15)	16,445	12,232
Operating lease liabilities (Note 14)	90,578	105,210
Regulatory liabilities (Note 4)	226,989	271,575
Other current liabilities	130,415	148,276
Total current liabilities	1,968,342	1,762,141
LONG-TERM DEBT LESS CURRENT MATURITIES (Note 3)	8,164,372	7,741,286
DEFERRED CREDITS AND OTHER
Deferred income taxes	2,408,218	2,384,421
Regulatory liabilities (Note 4)	1,919,281	2,061,776
Liabilities for asset retirements (Note 15)	878,735	785,530
Liabilities for pension benefits (Note 5)	110,472	116,286
Liabilities from risk management activities (Note 7)	13,012	4,749
Customer advances	520,180	422,103
Coal mine reclamation	182,816	179,255
Deferred investment tax credit	253,680	180,677
Unrecognized tax benefits	33,738	38,658
Operating lease liabilities (Note 14)	1,204,639	639,247
Other	288,736	247,400
Total deferred credits and other	7,813,507	7,060,102
COMMITMENTS AND CONTINGENCIES (Note 8)
EQUITY
Common stock, no par value; authorized 150,000,000 shares, 113,414,167 and 113,247,189 issued at respective dates	2,744,501	2,724,740
Treasury stock at cost; 75,767 and 73,613 shares at respective dates	(5,328)	(5,005)
Total common stock	2,739,173	2,719,735
Retained earnings	3,665,946	3,360,347
Accumulated other comprehensive loss (Note 13)	(30,434)	(31,435)
Total shareholder equity	6,374,685	6,048,647
Noncontrolling interests (Note 6)	113,520	111,229
Total equity	6,488,205	6,159,876
TOTAL LIABILITIES AND EQUITY	$ 24,434,426	$ 22,723,405