CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
NET INCOME	$ 126,182	$ 127,507	$ 135,508	$ 148,234
Derivative instruments:
Net unrealized gain (loss), net of tax benefit (expense)	128	25	(566)	(775)
Reclassification of net realized loss, net of tax benefit	624	874	1,766	2,850
Pension and other postretirement benefits activity, net of tax benefit (expense)	(701)	(117)	(171)	466
Total other comprehensive income	51	782	1,029	2,541
COMPREHENSIVE INCOME	126,233	128,289	136,537	150,775
Less: Comprehensive income attributable to noncontrolling interests	4,874	4,605	9,747	9,210
COMPREHENSIVE INCOME ATTRIBUTABLE TO COMMON SHAREHOLDERS	121,359	123,684	126,790	141,565
APS
NET INCOME	132,062	129,967	144,188	154,440
Derivative instruments:
Net unrealized gain (loss), net of tax benefit (expense)	128	25	(566)	(775)
Reclassification of net realized loss, net of tax benefit	624	874	1,766	2,850
Pension and other postretirement benefits activity, net of tax benefit (expense)	(642)	(74)	(31)	607
Total other comprehensive income	110	825	1,169	2,682
COMPREHENSIVE INCOME	132,172	130,792	145,357	157,122
Less: Comprehensive income attributable to noncontrolling interests	4,874	4,605	9,747	9,210
COMPREHENSIVE INCOME ATTRIBUTABLE TO COMMON SHAREHOLDERS	$ 127,298	$ 126,187	$ 135,610	$ 147,912