CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
CURRENT ASSETS
Cash and cash equivalents	$ 14,146	$ 59,968
Customer and other receivables	357,130	313,576
Accrued unbilled revenues	223,918	132,197
Allowance for doubtful accounts (Note 2)	(22,769)	(19,782)
Materials and supplies (at average cost)	340,672	314,745
Fossil fuel (at average cost)	25,074	19,552
Income tax receivable	0	6,792
Assets from risk management activities (Note 7)	82,309	2,931
Deferred fuel and purchased power regulatory asset (Note 4)	300,912	175,835
Other regulatory assets (Note 4)	119,890	115,878
Other current assets	81,901	76,627
Total current assets	1,523,183	1,198,319
INVESTMENTS AND OTHER ASSETS
Nuclear decommissioning trusts (Notes 11 and 12)	1,223,088	1,138,435
Other special use funds (Notes 11 and 12)	358,436	254,509
Other assets	112,091	92,922
Total investments and other assets	1,693,615	1,485,866
PROPERTY, PLANT AND EQUIPMENT
Plant in service and held for future use	21,236,805	20,837,885
Accumulated depreciation and amortization	(7,278,877)	(7,110,310)
Net	13,957,928	13,727,575
Construction work in progress	1,062,911	937,384
Palo Verde sale leaseback, net of accumulated depreciation (Note 6)	96,101	98,036
Intangible assets, net of accumulated amortization	279,911	282,570
Nuclear fuel, net of accumulated amortization	109,110	113,645
Total property, plant and equipment	15,505,961	15,159,210
DEFERRED DEBITS
Regulatory assets (Note 4)	1,173,977	1,133,987
Operating lease right-of-use assets (Note 15)	718,948	505,064
Assets for pension and other postretirement benefits (Note 5)	407,821	502,992
Other	38,073	34,983
Total deferred debits	2,338,819	2,177,026
TOTAL ASSETS	21,061,578	20,020,421
CURRENT LIABILITIES
Accounts payable	377,157	318,585
Accrued taxes	183,037	159,551
Accrued interest	56,864	56,962
Common dividends payable	93,610	93,531
Short-term borrowings (Note 3)	504,700	169,000
Current maturities of long-term debt (Note 3)	150,000	0
Customer deposits	44,419	48,340
Liabilities from risk management activities (Note 7)	1,512	7,557
Liabilities for asset retirements (Note 16)	15,646	15,586
Operating lease liabilities (Note 15)	128,673	74,785
Regulatory liabilities (Note 4)	327,612	229,088
Other current liabilities	140,038	187,448
Total current liabilities	2,023,268	1,360,433
Long-term debt less current maturities (Note 3)	6,315,927	6,314,266
DEFERRED CREDITS AND OTHER
Deferred income taxes	2,192,169	2,135,403
Regulatory liabilities (Note 4)	2,443,312	2,450,169
Liabilities for asset retirements (Note 16)	716,344	689,497
Liabilities for pension benefits (Note 5)	163,207	166,484
Liabilities from risk management activities (Note 7)	0	11,062
Customer advances	247,531	221,032
Coal mine reclamation	172,357	170,097
Deferred investment tax credit	187,720	191,372
Unrecognized tax benefits	6,002	5,834
Operating lease liabilities (Note 15)	547,164	361,336
Other	211,678	190,643
Total deferred credits and other	6,887,484	6,592,929
COMMITMENTS AND CONTINGENCIES (NOTE 8)
EQUITY
Common stock, no par value; authorized 150,000,000 shares, 112,819,703 and 112,760,051 issued at respective dates	2,692,015	2,677,482
Treasury stock at cost; 36,153 and 72,006 shares at respective dates	(3,079)	(6,289)
Total common stock	2,688,936	2,671,193
Retained earnings	3,089,266	3,025,106
Accumulated other comprehensive loss	(60,578)	(62,796)
Total shareholders’ equity	5,717,624	5,633,503
Noncontrolling interests (Note 6)	117,275	119,290
Total equity	5,834,899	5,752,793
TOTAL LIABILITIES AND EQUITY	21,061,578	20,020,421
APS
CURRENT ASSETS
Cash and cash equivalents	11,954	57,310
Customer and other receivables	357,023	312,644
Accrued unbilled revenues	223,918	132,197
Allowance for doubtful accounts (Note 2)	(22,769)	(19,782)
Materials and supplies (at average cost)	340,672	314,745
Fossil fuel (at average cost)	25,074	19,552
Assets from risk management activities (Note 7)	82,309	2,931
Deferred fuel and purchased power regulatory asset (Note 4)	300,912	175,835
Other regulatory assets (Note 4)	119,890	115,878
Other current assets	51,482	47,593
Total current assets	1,490,465	1,158,903
INVESTMENTS AND OTHER ASSETS
Nuclear decommissioning trusts (Notes 11 and 12)	1,223,088	1,138,435
Other special use funds (Notes 11 and 12)	358,436	254,509
Other assets	68,248	46,010
Total investments and other assets	1,649,772	1,438,954
PROPERTY, PLANT AND EQUIPMENT
Plant in service and held for future use	21,233,344	20,834,424
Accumulated depreciation and amortization	(7,275,617)	(7,107,058)
Net	13,957,727	13,727,366
Construction work in progress	1,062,911	937,384
Palo Verde sale leaseback, net of accumulated depreciation (Note 6)	96,101	98,036
Intangible assets, net of accumulated amortization	279,755	282,415
Nuclear fuel, net of accumulated amortization	109,110	113,645
Total property, plant and equipment	15,505,604	15,158,846
DEFERRED DEBITS
Regulatory assets (Note 4)	1,173,977	1,133,987
Operating lease right-of-use assets (Note 15)	717,411	503,475
Assets for pension and other postretirement benefits (Note 5)	400,414	495,673
Other	37,210	34,413
Total deferred debits	2,329,012	2,167,548
TOTAL ASSETS	20,974,853	19,924,251
CURRENT LIABILITIES
Accounts payable	369,905	311,699
Accrued taxes	193,409	148,970
Accrued interest	56,202	56,322
Common dividends payable	93,500	93,500
Short-term borrowings (Note 3)	495,000	0
Customer deposits	44,419	48,340
Liabilities from risk management activities (Note 7)	1,512	7,557
Liabilities for asset retirements (Note 16)	15,646	15,586
Operating lease liabilities (Note 15)	128,578	74,695
Regulatory liabilities (Note 4)	327,612	229,088
Other current liabilities	142,926	190,420
Total current liabilities	1,868,709	1,176,177
Long-term debt less current maturities (Note 3)	5,819,198	5,817,945
DEFERRED CREDITS AND OTHER
Deferred income taxes	2,192,580	2,143,673
Regulatory liabilities (Note 4)	2,443,312	2,450,169
Liabilities for asset retirements (Note 16)	716,344	689,497
Liabilities for pension benefits (Note 5)	146,728	148,943
Liabilities from risk management activities (Note 7)	0	11,062
Customer advances	247,531	221,032
Coal mine reclamation	172,357	170,097
Deferred investment tax credit	187,720	191,372
Unrecognized tax benefits	39,995	39,410
Operating lease liabilities (Note 15)	545,534	359,653
Other	182,555	160,036
Total deferred credits and other	6,874,656	6,584,944
COMMITMENTS AND CONTINGENCIES (NOTE 8)
EQUITY
Common stock	178,162	178,162
Additional paid-in capital	2,871,696	2,871,696
Retained earnings	3,284,989	3,216,955
Accumulated other comprehensive loss	(39,832)	(40,918)
Total shareholders’ equity	6,295,015	6,225,895
Noncontrolling interests (Note 6)	117,275	119,290
Total equity	6,412,290	6,345,185
Total capitalization	12,231,488	12,163,130
TOTAL LIABILITIES AND EQUITY	$ 20,974,853	$ 19,924,251