CONDENSED CONSOLIDATED STATEMENTS OF INCOME (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
OPERATING REVENUES	$ 740,530	$ 692,714
OPERATING EXPENSES
Fuel and purchased power	230,588	197,110
Operations and maintenance	245,634	265,682
Depreciation and amortization	148,707	144,825
Taxes other than income taxes	55,090	53,600
Other expenses	427	163
Total	680,446	661,380
OPERATING INCOME	60,084	31,334
OTHER INCOME (DEDUCTIONS)
Allowance for equity funds used during construction	11,188	14,079
Pension and other postretirement non-service credits - net	5,114	12,859
Other income (Note 9)	7,169	3,985
Other expense (Note 9)	(4,358)	(3,229)
Total	19,113	27,694
INTEREST EXPENSE
Interest charges	60,653	58,954
Allowance for borrowed funds used during construction	(6,665)	(6,755)
Total	53,988	52,199
INCOME BEFORE INCOME TAXES	25,209	6,829
INCOME TAXES	2,418	(1,265)
NET INCOME	22,791	8,094
Less: Net income attributable to noncontrolling interests (Note 6)	4,873	4,873
NET INCOME ATTRIBUTABLE TO COMMON SHAREHOLDERS	$ 17,918	$ 3,221
WEIGHTED-AVERAGE COMMON SHARES OUTSTANDING
WEIGHTED-AVERAGE COMMON SHARES OUTSTANDING - BASIC (in shares)	112,337	112,017
WEIGHTED-AVERAGE COMMON SHARES OUTSTANDING - DILUTED (in shares)	112,735	112,493
EARNINGS PER WEIGHTED-AVERAGE COMMON SHARE OUTSTANDING
Net income attributable to common shareholders - basic (in dollars per share)	$ 0.16	$ 0.03
Net income attributable to common shareholders - diluted (in dollars per share)	$ 0.16	$ 0.03
APS
OPERATING REVENUES	$ 740,530	$ 692,006
OPERATING EXPENSES
Fuel and purchased power	230,588	202,010
Operations and maintenance	240,375	254,601
Depreciation and amortization	148,685	144,112
Taxes other than income taxes	55,078	53,242
Other expenses	427	163
Total	675,153	654,128
OPERATING INCOME	65,377	37,878
OTHER INCOME (DEDUCTIONS)
Allowance for equity funds used during construction	11,188	14,079
Pension and other postretirement non-service credits - net	5,499	13,197
Other income (Note 9)	6,416	3,772
Other expense (Note 9)	(3,878)	(2,945)
Total	19,225	28,103
INTEREST EXPENSE
Interest charges	56,665	56,158
Allowance for borrowed funds used during construction	(6,665)	(6,755)
Total	50,000	49,403
INCOME BEFORE INCOME TAXES	34,602	16,578
INCOME TAXES	1,453	2,106
NET INCOME	33,149	14,472
Less: Net income attributable to noncontrolling interests (Note 6)	4,873	4,873
NET INCOME ATTRIBUTABLE TO COMMON SHAREHOLDERS	$ 28,276	$ 9,599