CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
CURRENT ASSETS
Cash and cash equivalents	$ 6,763	$ 10,283
Customer and other receivables	279,480	266,426
Accrued unbilled revenues	191,578	128,165
Allowance for doubtful accounts	(11,579)	(8,171)
Materials and supplies (at average cost)	318,368	331,091
Fossil fuel (at average cost)	17,257	14,829
Income tax receivable	17,122	21,727
Assets from risk management activities (Note 7)	710	515
Deferred fuel and purchased power regulatory asset (Note 4)	101,425	70,137
Other regulatory assets (Note 4)	150,169	133,070
Other current assets	75,796	61,958
Total current assets	1,147,089	1,030,030
INVESTMENTS AND OTHER ASSETS
Nuclear decommissioning trust (Notes 11 and 12)	1,024,033	1,010,775
Other special use funds (Notes 11 and 12)	253,332	245,095
Other assets	92,295	96,953
Total investments and other assets	1,369,660	1,352,823
PROPERTY, PLANT AND EQUIPMENT
Plant in service and held for future use	20,343,151	19,836,292
Accumulated depreciation and amortization	(6,905,049)	(6,637,857)
Net	13,438,102	13,198,435
Construction work in progress	823,691	808,133
Intangible assets, net of accumulated amortization	275,028	290,564
Nuclear fuel, net of accumulated amortization	152,219	123,500
Total property, plant and equipment	14,789,011	14,522,538
DEFERRED DEBITS
Regulatory assets (Note 4)	1,315,846	1,304,073
Operating lease right-of-use assets (Note 16)	555,783	145,813
Assets for other postretirement benefits (Note 5)	99,801	90,570
Other	30,198	33,400
Total deferred debits	2,001,628	1,573,856
TOTAL ASSETS	19,307,388	18,479,247
CURRENT LIABILITIES
Current maturities of long-term debt (Note 3)	0	800,000
Accounts payable	316,230	346,448
Accrued taxes	151,487	144,899
Accrued interest	53,503	53,534
Common dividends payable	88,066	87,982
Short-term borrowings (Note 3)	291,900	114,675
Customer deposits	49,132	64,908
Liabilities from risk management activities (Note 7)	44,805	38,946
Liabilities for asset retirements	10,735	11,025
Operating lease liabilities (Note 16)	83,851	12,713
Regulatory liabilities (Note 4)	279,479	234,912
Other current liabilities	127,175	168,323
Total current liabilities	1,496,363	2,078,365
Long-term debt less current maturities (Note 3)	5,922,161	4,832,558
DEFERRED CREDITS AND OTHER
Deferred income taxes	2,070,453	1,992,339
Regulatory liabilities (Note 4)	2,089,987	2,267,835
Liabilities for asset retirements	657,217	646,193
Liabilities for pension benefits (Note 5)	284,585	280,185
Liabilities from risk management activities (Note 7)	26,181	33,186
Customer advances	213,572	215,330
Unrecorded Unconditional Purchase Obligation	167,896	165,695
Deferred investment tax credit	193,081	196,468
Unrecognized tax benefits	6,613	6,189
Operating lease liabilities (Note 16)	409,621	51,872
Other	159,181	159,844
Total deferred credits and other	6,278,387	6,015,136
COMMITMENTS AND CONTINGENCIES (SEE NOTE 8)
EQUITY
Common stock, no par value; authorized 150,000,000 shares, 112,591,124 and 112,540,126 issued at respective dates	2,665,518	2,659,561
Treasury stock at cost; 35,983 and 103,546 shares at respective dates	(3,190)	(9,427)
Total common stock	2,662,328	2,650,134
Retained earnings	2,885,109	2,837,610
Accumulated other comprehensive loss	(57,875)	(57,096)
Total shareholders’ equity	5,489,562	5,430,648
Noncontrolling interests (Note 6)	120,915	122,540
Total equity	5,610,477	5,553,188
TOTAL LIABILITIES AND EQUITY	19,307,388	18,479,247
APS
CURRENT ASSETS
Cash and cash equivalents	6,224	10,169
Customer and other receivables	275,476	255,479
Accrued unbilled revenues	191,578	128,165
Allowance for doubtful accounts	(11,579)	(8,171)
Materials and supplies (at average cost)	318,368	331,091
Fossil fuel (at average cost)	17,257	14,829
Income tax receivable	0	7,313
Assets from risk management activities (Note 7)	710	515
Deferred fuel and purchased power regulatory asset (Note 4)	101,425	70,137
Other regulatory assets (Note 4)	150,169	133,070
Other current assets	47,588	38,895
Total current assets	1,097,216	981,492
INVESTMENTS AND OTHER ASSETS
Nuclear decommissioning trust (Notes 11 and 12)	1,024,033	1,010,775
Other special use funds (Notes 11 and 12)	253,332	245,095
Other assets	43,973	43,781
Total investments and other assets	1,321,338	1,299,651
PROPERTY, PLANT AND EQUIPMENT
Plant in service and held for future use	20,339,690	19,832,805
Accumulated depreciation and amortization	(6,901,805)	(6,634,597)
Net	13,437,885	13,198,208
Construction work in progress	823,691	808,133
Intangible assets, net of accumulated amortization	274,873	290,409
Nuclear fuel, net of accumulated amortization	152,219	123,500
Total property, plant and equipment	14,788,639	14,522,156
DEFERRED DEBITS
Regulatory assets (Note 4)	1,315,846	1,304,073
Operating lease right-of-use assets (Note 16)	554,106	144,024
Assets for other postretirement benefits (Note 5)	95,937	86,736
Other	29,562	32,591
Total deferred debits	1,995,451	1,567,424
TOTAL ASSETS	19,202,644	18,370,723
CURRENT LIABILITIES
Current maturities of long-term debt (Note 3)	0	350,000
Accounts payable	307,931	338,006
Accrued taxes	150,879	136,328
Accrued interest	52,925	52,619
Common dividends payable	88,000	88,000
Short-term borrowings (Note 3)	219,900	0
Customer deposits	49,132	64,908
Liabilities from risk management activities (Note 7)	44,805	38,946
Liabilities for asset retirements	10,735	11,025
Operating lease liabilities (Note 16)	83,744	12,549
Regulatory liabilities (Note 4)	279,479	234,912
Other current liabilities	128,147	164,736
Total current liabilities	1,415,677	1,492,029
Long-term debt less current maturities (Note 3)	5,425,551	4,833,133
DEFERRED CREDITS AND OTHER
Deferred income taxes	2,106,268	2,033,096
Regulatory liabilities (Note 4)	2,089,987	2,267,835
Liabilities for asset retirements	657,217	646,193
Liabilities for pension benefits (Note 5)	267,386	262,243
Liabilities from risk management activities (Note 7)	26,181	33,186
Customer advances	213,572	215,330
Unrecorded Unconditional Purchase Obligation	167,896	165,695
Deferred investment tax credit	193,081	196,468
Unrecognized tax benefits	39,039	40,188
Operating lease liabilities (Note 16)	407,888	50,092
Other	138,764	136,432
Total deferred credits and other	6,307,279	6,046,758
COMMITMENTS AND CONTINGENCIES (SEE NOTE 8)
EQUITY
Common stock	178,162	178,162
Additional paid-in capital	2,721,696	2,721,696
Retained earnings	3,068,389	3,011,927
Accumulated other comprehensive loss	(35,025)	(35,522)
Total shareholders’ equity	5,933,222	5,876,263
Noncontrolling interests (Note 6)	120,915	122,540
Total equity	6,054,137	5,998,803
Total capitalization	11,479,688	10,831,936
TOTAL LIABILITIES AND EQUITY	19,202,644	18,370,723
Variable Interest Entity
PROPERTY, PLANT AND EQUIPMENT
Total property, plant and equipment	99,971	101,906
Variable Interest Entity | APS
PROPERTY, PLANT AND EQUIPMENT
Total property, plant and equipment	99,971	101,906
EQUITY
Noncontrolling interests (Note 6)	$ 120,915	$ 122,540