CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
CASH FLOWS FROM OPERATING ACTIVITIES
NET INCOME	$ 179,706	$ 200,502
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization including nuclear fuel	325,550	291,285
Deferred fuel and purchased power	(50,112)	(21,993)
Deferred fuel and purchased power amortization	50,851	(13,663)
Allowance for equity funds used during construction	(27,152)	(19,938)
Deferred income taxes	33,711	94,365
Deferred investment tax credit	(2,778)	(3,194)
Change in derivative instruments fair value	0	(222)
Stock compensation	13,189	12,891
Changes in current assets and liabilities:
Customer and other receivables	(18,672)	(62,624)
Accrued unbilled revenues	(95,453)	(105,754)
Materials, supplies and fossil fuel	(22,970)	(5,437)
Income tax receivable	0	(322)
Other current assets	11,069	(23,418)
Accounts payable	36,614	21,771
Accrued taxes	8,140	11,745
Other current liabilities	9,410	(44,778)
Change in margin and collateral accounts — assets	(920)	(71)
Change in margin and collateral accounts — liabilities	(1,082)	(4,700)
Change in other long-term assets	24,847	(49,162)
Change in other long-term liabilities	(78,146)	13,279
Net cash flow provided by operating activities	395,802	290,562
CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures	(679,949)	(693,626)
Contributions in aid of construction	19,339	18,032
Allowance for borrowed funds used during construction	(13,046)	(9,378)
Proceeds from nuclear decommissioning trust sales and other special use funds	258,401	275,364
Investment in nuclear decommissioning trust and other special use funds	(259,542)	(276,505)
Other	(4,299)	(2,127)
Net cash flow used for investing activities	(679,096)	(688,240)
CASH FLOWS FROM FINANCING ACTIVITIES
Issuance of long-term debt	0	251,635
Short-term borrowing and payments — net	500,849	287,800
Short-term debt borrowings under revolving credit facility	45,000	17,000
Short-term debt repayments under revolving credit facility	(25,000)	0
Repayment of long-term debt	(82,000)	0
Dividends paid on common stock	(151,942)	(142,520)
Common stock equity issuance - net of purchases	(2,294)	(8,792)
Distributions to noncontrolling interests	(11,372)	(11,372)
Other	0	(1)
Net cash flow provided by financing activities	273,241	393,750
NET DECREASE IN CASH AND CASH EQUIVALENTS	(10,053)	(3,928)
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD	13,892	8,881
CASH AND CASH EQUIVALENTS AT END OF PERIOD	3,839	4,953
Supplemental disclosure of cash flow information
Income taxes, net of refunds	10,032	2,062
Interest, net of amounts capitalized	104,249	94,870
Significant non-cash investing and financing activities:
Accrued capital expenditures	65,995	80,517
Dividends declared but not yet paid	77,821	73,113
APS
CASH FLOWS FROM OPERATING ACTIVITIES
NET INCOME	197,170	202,017
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization including nuclear fuel	323,934	290,444
Deferred fuel and purchased power	(50,112)	(21,994)
Deferred fuel and purchased power amortization	50,851	(13,663)
Allowance for equity funds used during construction	(27,152)	(19,938)
Deferred income taxes	10,372	87,412
Deferred investment tax credit	(2,778)	(3,194)
Change in derivative instruments fair value	0	(222)
Changes in current assets and liabilities:
Customer and other receivables	(9,254)	(41,422)
Accrued unbilled revenues	(95,453)	(105,754)
Materials, supplies and fossil fuel	(23,073)	(5,333)
Income tax receivable	0	11,174
Other current assets	7,552	(20,039)
Accounts payable	39,573	20,147
Accrued taxes	26,412	16,759
Other current liabilities	7,395	(33,408)
Change in margin and collateral accounts — assets	(920)	(71)
Change in margin and collateral accounts — liabilities	(1,082)	(4,700)
Change in other long-term assets	35,867	(45,420)
Change in other long-term liabilities	(83,561)	13,061
Net cash flow provided by operating activities	405,741	325,856
CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures	(670,841)	(680,343)
Contributions in aid of construction	19,339	18,032
Allowance for borrowed funds used during construction	(13,046)	(9,378)
Proceeds from nuclear decommissioning trust sales and other special use funds	258,227	275,364
Investment in nuclear decommissioning trust and other special use funds	(259,367)	(276,505)
Other	(1,221)	(1,478)
Net cash flow used for investing activities	(666,909)	(674,308)
CASH FLOWS FROM FINANCING ACTIVITIES
Issuance of long-term debt	0	251,635
Short-term borrowing and payments — net	499,949	250,200
Short-term debt borrowings under revolving credit facility	25,000	0
Short-term debt repayments under revolving credit facility	(25,000)	0
Repayment of long-term debt	(82,000)	0
Dividends paid on common stock	(155,500)	(146,000)
Distributions to noncontrolling interests	(11,372)	(11,372)
Net cash flow provided by financing activities	251,077	344,463
NET DECREASE IN CASH AND CASH EQUIVALENTS	(10,091)	(3,989)
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD	13,851	8,840
CASH AND CASH EQUIVALENTS AT END OF PERIOD	3,760	4,851
Supplemental disclosure of cash flow information
Income taxes, net of refunds	24,689	1
Interest, net of amounts capitalized	98,478	92,334
Significant non-cash investing and financing activities:
Accrued capital expenditures	65,995	82,621
Dividends declared but not yet paid	$ 77,800	$ 73,100