CONDENSED CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
OPERATING REVENUES (NOTE 2)	$ 696,475	$ 661,930
OPERATING EXPENSES
Fuel and purchased power	198,227	188,521
Operations and maintenance	230,055	221,318
Depreciation and amortization	157,820	154,079
Taxes other than income taxes	59,483	56,768
Other expenses	3,356	822
Total	648,941	621,508
OPERATING INCOME	47,534	40,422
OTHER INCOME (DEDUCTIONS)
Allowance for equity funds used during construction	9,207	7,697
Pension and other postretirement non-service credits — net	27,791	13,911
Other income (Note 9)	12,429	12,569
Other expense (Note 9)	(3,853)	(4,784)
Total	45,574	29,393
INTEREST EXPENSE
Interest charges	61,938	59,234
Allowance for borrowed funds used during construction	(4,994)	(4,076)
Total	56,944	55,158
INCOME BEFORE INCOME TAXES	36,164	14,657
INCOME TAXES	(4,350)	(20,209)
NET INCOME	40,514	34,866
Less: Comprehensive income attributable to noncontrolling interests	4,873	4,873
NET INCOME ATTRIBUTABLE TO COMMON SHAREHOLDERS	$ 35,641	$ 29,993
WEIGHTED-AVERAGE COMMON SHARES OUTSTANDING
WEIGHTED-AVERAGE COMMON SHARES OUTSTANDING - BASIC (in shares)	112,829	112,594
WEIGHTED-AVERAGE COMMON SHARES OUTSTANDING - DILUTED (in shares)	113,093	112,862
EARNINGS PER WEIGHTED-AVERAGE COMMON SHARE OUTSTANDING
Net income attributable to common shareholders - basic (in dollars per share)	$ 0.32	$ 0.27
Net income attributable to common shareholders - diluted (in dollars per share)	$ 0.32	$ 0.27
APS
OPERATING REVENUES (NOTE 2)	$ 696,475	$ 661,930
OPERATING EXPENSES
Fuel and purchased power	198,227	188,521
Operations and maintenance	226,401	218,265
Depreciation and amortization	157,800	154,058
Taxes other than income taxes	59,472	56,758
Other expenses	3,356	822
Total	645,256	618,424
OPERATING INCOME	51,219	43,506
OTHER INCOME (DEDUCTIONS)
Allowance for equity funds used during construction	9,207	7,697
Pension and other postretirement non-service credits — net	27,837	14,262
Other income (Note 9)	11,960	11,633
Other expense (Note 9)	(3,350)	(4,668)
Total	45,654	28,924
INTEREST EXPENSE
Interest charges	59,388	55,736
Allowance for borrowed funds used during construction	(4,994)	(4,076)
Total	54,394	51,660
INCOME BEFORE INCOME TAXES	42,479	20,770
INCOME TAXES	2,319	(19,448)
NET INCOME	40,160	40,218
Less: Comprehensive income attributable to noncontrolling interests	4,873	4,873
NET INCOME ATTRIBUTABLE TO COMMON SHAREHOLDERS	$ 35,287	$ 35,345