CONDENSED CONSOLIDATED STATEMENTS OF INCOME (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
OPERATING REVENUES	$ 974,123	$ 944,587	$ 1,666,837	$ 1,622,315
OPERATING EXPENSES
Fuel and purchased power	257,087	254,611	454,197	467,006
Operations and maintenance	268,397	220,985	534,079	447,056
Depreciation and amortization	145,436	125,739	290,261	253,366
Taxes other than income taxes	53,607	44,289	107,207	88,125
Other expenses	7,434	1,706	7,597	2,094
Total	731,961	647,330	1,393,341	1,257,647
OPERATING INCOME	242,162	297,257	273,496	364,668
OTHER INCOME (DEDUCTIONS)
Allowance for equity funds used during construction	13,073	10,456	27,152	19,938
Pension and other postretirement non-service credits - net	12,006	6,972	24,865	13,067
Other income (Note 9)	6,598	484	10,583	964
Other expense (Note 9)	(3,771)	(3,822)	(7,000)	(7,502)
Total	27,906	14,090	55,600	26,467
INTEREST EXPENSE
Interest charges	60,708	54,969	119,662	106,833
Allowance for borrowed funds used during construction	(6,291)	(4,906)	(13,046)	(9,378)
Total	54,417	50,063	106,616	97,455
INCOME BEFORE INCOME TAXES	215,651	261,284	222,480	293,680
INCOME TAXES	44,039	88,967	42,774	93,178
NET INCOME	171,612	172,317	179,706	200,502
Less: Net income attributable to noncontrolling interests (Note 6)	4,874	4,874	9,747	9,747
NET INCOME ATTRIBUTABLE TO COMMON SHAREHOLDERS	$ 166,738	$ 167,443	$ 169,959	$ 190,755
WEIGHTED-AVERAGE COMMON SHARES OUTSTANDING
WEIGHTED-AVERAGE COMMON SHARES OUTSTANDING - BASIC (in shares)	112,115	111,797	112,067	111,763
WEIGHTED-AVERAGE COMMON SHARES OUTSTANDING - DILUTED (in shares)	112,471	112,345	112,482	112,270
EARNINGS PER WEIGHTED-AVERAGE COMMON SHARE OUTSTANDING
Net income attributable to common shareholders - basic (in dollars per share)	$ 1.49	$ 1.50	$ 1.52	$ 1.71
Net income attributable to common shareholders - diluted (in dollars per share)	1.48	1.49	1.51	1.70
DIVIDENDS DECLARED PER SHARE (in dollars per share)	$ 1.39	$ 1.31	$ 1.39	$ 1.31
APS
OPERATING REVENUES	$ 971,963	$ 943,406	$ 1,663,969	$ 1,620,995
OPERATING EXPENSES
Fuel and purchased power	270,138	259,892	472,148	476,995
Operations and maintenance	251,999	215,775	506,600	434,783
Depreciation and amortization	144,533	125,317	288,645	252,524
Taxes other than income taxes	53,269	44,016	106,511	87,580
Other expenses	434	1,706	597	2,142
Total	720,373	646,706	1,374,501	1,254,024
OPERATING INCOME	251,590	296,700	289,468	366,971
OTHER INCOME (DEDUCTIONS)
Allowance for equity funds used during construction	13,073	10,456	27,152	19,938
Pension and other postretirement non-service credits - net	12,389	6,911	25,586	12,953
Other income (Note 9)	6,235	352	10,007	694
Other expense (Note 9)	(3,372)	(3,301)	(6,318)	(6,429)
Total	28,325	14,418	56,427	27,156
INTEREST EXPENSE
Interest charges	57,731	53,517	113,889	104,313
Allowance for borrowed funds used during construction	(6,291)	(4,906)	(13,046)	(9,378)
Total	51,440	48,611	100,843	94,935
INCOME BEFORE INCOME TAXES	228,475	262,507	245,052	299,192
INCOME TAXES	45,776	88,525	47,882	97,175
NET INCOME	182,699	173,982	197,170	202,017
Less: Net income attributable to noncontrolling interests (Note 6)	4,874	4,874	9,747	9,747
NET INCOME ATTRIBUTABLE TO COMMON SHAREHOLDERS	$ 177,825	$ 169,108	$ 187,423	$ 192,270