CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
CURRENT ASSETS
Cash and cash equivalents	$ 6,951	$ 4,832
Customer and other receivables	449,096	453,209
Accrued unbilled revenues	143,276	164,764
Allowance for doubtful accounts (Note 2)	(22,112)	(23,778)
Materials and supplies (at average cost)	425,457	410,481
Income tax receivable	11,699	14,086
Fossil fuel (at average cost)	39,571	40,155
Assets from risk management activities (Note 7)	16,095	87,835
Deferred fuel and purchased power regulatory asset (Note 4)	469,962	460,561
Other regulatory assets (Note 4)	130,840	78,318
Other current assets	77,551	60,091
Total current assets	1,748,386	1,750,554
INVESTMENTS AND OTHER ASSETS
Nuclear decommissioning trusts (Notes 11 and 12)	1,125,617	1,073,410
Other special use funds (Notes 11 and 12)	352,877	347,231
Assets from risk management activities (Note 7)	17,082	44,394
Other assets	147,430	125,672
Total investments and other assets	1,643,006	1,590,707
PROPERTY, PLANT AND EQUIPMENT
Plant in service and held for future use	22,624,104	22,452,146
Accumulated depreciation and amortization	(8,072,595)	(7,929,878)
Net	14,551,509	14,522,268
Construction work in progress	2,101,830	1,882,791
Palo Verde sale leaseback, net of accumulated depreciation (Note 6)	89,329	90,296
Intangible assets, net of accumulated amortization	260,454	258,880
Nuclear fuel, net of accumulated amortization	112,735	100,119
Total property, plant and equipment	17,115,857	16,854,354
DEFERRED DEBITS
Regulatory assets (Note 4)	1,258,663	1,283,221
Operating lease right-of-use assets	1,361,847	801,688
Assets for pension and other postretirement benefits (Note 5)	405,409	396,599
Other	47,205	46,282
Total deferred debits	3,073,124	2,527,790
TOTAL ASSETS	23,580,373	22,723,405
CURRENT LIABILITIES
Accounts payable	361,410	430,425
Accrued taxes	214,484	164,440
Accrued interest	72,146	61,217
Common dividends payable	0	97,895
Short-term borrowings (Note 3)	497,550	340,720
Current maturities of long-term debt (Note 3)	60,821	50,685
Customer deposits	41,186	41,769
Liabilities from risk management activities (Note 7)	83,874	37,697
Liabilities for asset retirements	20,321	12,232
Operating lease liabilities	65,130	105,210
Less: current regulatory liabilities	202,266	271,575
Other current liabilities	105,141	148,276
Total current liabilities	1,724,329	1,762,141
LONG-TERM DEBT LESS CURRENT MATURITIES (Note 3)	7,916,554	7,741,286
DEFERRED CREDITS AND OTHER
Deferred income taxes	2,379,720	2,384,421
Total non-current regulatory liabilities	2,060,273	2,061,776
Liabilities for asset retirements	787,220	785,530
Liabilities for pension benefits (Note 5)	114,290	116,286
Customer advances	532,596	422,103
Coal mine reclamation	180,446	179,255
Deferred investment tax credit	184,427	180,677
Unrecognized tax benefits	38,863	38,658
Operating lease liabilities	1,240,584	639,247
Other	256,620	252,149
Total deferred credits and other	7,775,039	7,060,102
COMMITMENTS AND CONTINGENCIES (Note 8)
EQUITY
Common stock, no par value; authorized 150,000,000 shares, 113,359,467 and 113,247,189 issued at respective dates	2,730,851	2,724,740
Treasury stock at cost; 106,141 and 73,613 shares at respective dates	(7,451)	(5,005)
Total common stock	2,723,400	2,719,735
Retained earnings	3,357,052	3,360,347
Accumulated other comprehensive loss (Note 13)	(31,536)	(31,435)
Total shareholders’ equity	6,048,916	6,048,647
Noncontrolling interests (Note 6)	115,535	111,229
Total equity	6,164,451	6,159,876
TOTAL LIABILITIES AND EQUITY	$ 23,580,373	$ 22,723,405