CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
NET INCOME	$ 8,094	$ 28,185
Derivative instruments:
Net unrealized gain (loss), net of tax expense	(96)	(770)
Reclassification of net realized loss, net of tax expense	409	1,207
Pension and other postretirement benefits activity, net of tax expense	900	522
Total other comprehensive income	1,213	959
COMPREHENSIVE INCOME	9,307	29,144
Less: Comprehensive income attributable to noncontrolling interests	4,873	4,873
COMPREHENSIVE INCOME ATTRIBUTABLE TO COMMON SHAREHOLDERS	4,434	24,271
APS
NET INCOME	14,472	28,035
Derivative instruments:
Net unrealized gain (loss), net of tax expense	(96)	(770)
Reclassification of net realized loss, net of tax expense	409	1,207
Pension and other postretirement benefits activity, net of tax expense	857	611
Total other comprehensive income	1,170	1,048
COMPREHENSIVE INCOME	15,642	29,083
Less: Comprehensive income attributable to noncontrolling interests	4,873	4,873
COMPREHENSIVE INCOME ATTRIBUTABLE TO COMMON SHAREHOLDERS	$ 10,769	$ 24,210