CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
NET INCOME	$ 40,514	$ 34,866
Derivative instruments:
Net unrealized gain, net of tax benefit (expense)	262	292
Reclassification of net realized gain, net of tax benefit (expense)	0	20
Pension and other postretirement benefits activity, net of tax expense	1,022	1,205
Total other comprehensive income	1,284	1,517
COMPREHENSIVE INCOME	41,798	36,383
Less: Comprehensive income attributable to noncontrolling interests	4,873	4,873
COMPREHENSIVE INCOME ATTRIBUTABLE TO COMMON SHAREHOLDERS	36,925	31,510
APS
NET INCOME	40,160	40,218
Derivative instruments:
Net unrealized gain, net of tax benefit (expense)	0	292
Reclassification of net realized gain, net of tax benefit (expense)	0	20
Pension and other postretirement benefits activity, net of tax expense	927	1,013
Total other comprehensive income	927	1,325
COMPREHENSIVE INCOME	41,087	41,543
Less: Comprehensive income attributable to noncontrolling interests	4,873	4,873
COMPREHENSIVE INCOME ATTRIBUTABLE TO COMMON SHAREHOLDERS	$ 36,214	$ 36,670