CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
CURRENT ASSETS
Cash and cash equivalents	$ 1,648	$ 5,766
Customer and other receivables	263,836	267,887
Accrued unbilled revenues	193,657	137,170
Allowance for doubtful accounts	(3,095)	(4,069)
Materials and supplies (at average cost)	289,928	269,065
Fossil fuel (at average cost)	25,453	25,029
Assets from risk management activities (Note 7)	459	1,113
Deferred fuel and purchased power regulatory asset (Note 4)	30,559	37,164
Other regulatory assets (Note 4)	153,900	129,738
Other current assets	72,222	56,128
Total current assets	1,028,567	924,991
INVESTMENTS AND OTHER ASSETS
Nuclear decommissioning trust (Notes 11 and 12)	950,448	851,134
Other special use funds (Notes 11 and 12)	241,558	236,101
Other assets	97,322	103,247
Total investments and other assets	1,289,328	1,190,482
PROPERTY, PLANT AND EQUIPMENT
Plant in service and held for future use	19,630,407	18,736,628
Accumulated depreciation and amortization	(6,470,935)	(6,366,014)
Net	13,159,472	12,370,614
Construction work in progress	568,890	1,170,062
Palo Verde sale leaseback, net of accumulated depreciation (Note 6)	103,841	105,775
Intangible assets, net of accumulated amortization	261,584	262,902
Nuclear fuel, net of accumulated amortization	159,633	120,217
Total property, plant and equipment	14,253,420	14,029,570
DEFERRED DEBITS
Regulatory assets (Note 4)	1,321,431	1,342,941
Operating lease right-of-use assets (Note 16)	176,219	0
Assets for other postretirement benefits (Note 5)	56,336	46,906
Other	40,365	129,312
Total deferred debits	1,594,351	1,519,159
TOTAL ASSETS	18,165,666	17,664,202
CURRENT LIABILITIES
Accounts payable	327,969	277,336
Accrued taxes	158,921	154,819
Accrued interest	50,581	61,107
Common dividends payable	82,824	82,675
Short-term borrowings (Note 3)	432,373	76,400
Current maturities of long-term debt (Note 3)	250,000	500,000
Customer deposits	84,177	91,174
Liabilities from risk management activities (Note 7)	58,834	35,506
Liabilities for asset retirements	21,950	19,842
Operating lease liabilities (Note 16)	60,596	0
Regulatory liabilities (Note 4)	231,857	165,876
Other current liabilities	140,879	184,229
Total current liabilities	1,900,961	1,648,964
DEFERRED CREDITS AND OTHER
Deferred income taxes	1,838,145	1,807,421
Regulatory liabilities (Note 4)	2,287,892	2,325,976
Liabilities for asset retirements	723,005	706,703
Liabilities for pension benefits (Note 5)	356,928	443,170
Liabilities from risk management activities (Note 7)	21,592	24,531
Customer advances	174,411	137,153
Coal mine reclamation	197,443	212,785
Deferred investment tax credit	197,749	200,405
Unrecognized tax benefits	26,271	22,517
Operating lease liabilities (Note 16)	53,005	0
Other	144,142	147,640
Total deferred credits and other	6,020,583	6,028,301
COMMITMENTS AND CONTINGENCIES (SEE NOTE 8)
EQUITY
Common stock, no par value; authorized 150,000,000 shares, 112,361,595 and 112,159,896 issued at respective dates	2,648,234	2,634,265
Treasury stock at cost; 58,219 and 58,135 shares at respective dates	(5,140)	(4,825)
Total common stock	2,643,094	2,629,440
Retained earnings	2,637,620	2,641,183
Accumulated other comprehensive loss	(47,636)	(47,708)
Total shareholders’ equity	5,233,078	5,222,915
Noncontrolling interests (Note 6)	124,165	125,790
Total equity	5,357,243	5,348,705
Long-term debt less current maturities (Note 3)	4,886,879	4,638,232
TOTAL LIABILITIES AND EQUITY	18,165,666	17,664,202
APS
CURRENT ASSETS
Cash and cash equivalents	1,355	5,707
Customer and other receivables	253,501	257,654
Accrued unbilled revenues	193,657	137,170
Allowance for doubtful accounts	(3,095)	(4,069)
Materials and supplies (at average cost)	289,928	269,065
Fossil fuel (at average cost)	25,453	25,029
Assets from risk management activities (Note 7)	459	1,113
Deferred fuel and purchased power regulatory asset (Note 4)	30,559	37,164
Other regulatory assets (Note 4)	153,900	129,738
Other current assets	49,697	35,111
Total current assets	995,414	893,682
INVESTMENTS AND OTHER ASSETS
Nuclear decommissioning trust (Notes 11 and 12)	950,448	851,134
Other special use funds (Notes 11 and 12)	241,558	236,101
Other assets	46,089	40,817
Total investments and other assets	1,238,095	1,128,052
PROPERTY, PLANT AND EQUIPMENT
Plant in service and held for future use	19,626,920	18,733,142
Accumulated depreciation and amortization	(6,467,684)	(6,362,771)
Net	13,159,236	12,370,371
Construction work in progress	568,890	1,170,062
Palo Verde sale leaseback, net of accumulated depreciation (Note 6)	103,841	105,775
Intangible assets, net of accumulated amortization	261,429	262,746
Nuclear fuel, net of accumulated amortization	159,633	120,217
Total property, plant and equipment	14,253,029	14,029,171
DEFERRED DEBITS
Regulatory assets (Note 4)	1,321,431	1,342,941
Operating lease right-of-use assets (Note 16)	174,320	0
Assets for other postretirement benefits (Note 5)	52,611	43,212
Other	39,523	128,265
Total deferred debits	1,587,885	1,514,418
TOTAL ASSETS	18,074,423	17,565,323
CURRENT LIABILITIES
Accounts payable	319,435	266,277
Accrued taxes	175,922	176,357
Accrued interest	49,703	60,228
Common dividends payable	82,800	82,700
Short-term borrowings (Note 3)	376,873	0
Current maturities of long-term debt (Note 3)	250,000	500,000
Customer deposits	84,177	91,174
Liabilities from risk management activities (Note 7)	58,834	35,506
Liabilities for asset retirements	21,950	19,842
Operating lease liabilities (Note 16)	60,395	0
Regulatory liabilities (Note 4)	231,857	165,876
Other current liabilities	138,423	178,137
Total current liabilities	1,850,369	1,576,097
DEFERRED CREDITS AND OTHER
Deferred income taxes	1,831,660	1,812,664
Regulatory liabilities (Note 4)	2,287,892	2,325,976
Liabilities for asset retirements	723,005	706,703
Liabilities for pension benefits (Note 5)	340,154	425,404
Liabilities from risk management activities (Note 7)	21,592	24,531
Customer advances	174,411	137,153
Coal mine reclamation	197,443	212,785
Deferred investment tax credit	197,749	200,405
Unrecognized tax benefits	42,313	41,861
Operating lease liabilities (Note 16)	51,158	0
Other	121,052	125,511
Total deferred credits and other	5,988,429	6,012,993
COMMITMENTS AND CONTINGENCIES (SEE NOTE 8)
EQUITY
Total common stock	178,162	178,162
Additional paid-in capital	2,721,696	2,721,696
Retained earnings	2,801,110	2,788,256
Accumulated other comprehensive loss	(27,276)	(27,107)
Total shareholders’ equity	5,673,692	5,661,007
Noncontrolling interests (Note 6)	124,165	125,790
Total equity	5,797,857	5,786,797
Long-term debt less current maturities (Note 3)	4,437,768	4,189,436
Total capitalization	10,235,625	9,976,233
TOTAL LIABILITIES AND EQUITY	$ 18,074,423	$ 17,565,323