Changes in Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period			$ 4,935,912	$ 4,719,457
Total other comprehensive income	$ 1,509	$ 1,573	1,705	2,602
Balance at end of period	5,277,607	4,992,135	5,277,607	4,992,135
AOCI Including Portion Attributable to Noncontrolling Interest
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(43,626)	(43,719)	(43,822)	(44,748)
Balance at end of period	(42,117)	(42,146)	(42,117)	(42,146)
Accumulated Net Gain (Loss) from Cash Flow Hedges Including Portion Attributable to Noncontrolling Interest
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
OCI (loss) before reclassifications	9	(29)	(754)	(595)
Amounts reclassified from accumulated other comprehensive loss	710	798	2,480	2,564
Total other comprehensive income	719	769	1,726	1,969
Accumulated Defined Benefit Plans Adjustment Including Portion Attributable to Noncontrolling Interest
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
OCI (loss) before reclassifications	0	0	(2,157)	(1,585)
Amounts reclassified from accumulated other comprehensive loss	790	804	2,136	2,218
Total other comprehensive income	790	804	(21)	633
Arizona Public Service Company
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period			5,037,970	4,814,794
Total other comprehensive income	1,496	1,568	1,807	2,737
Balance at end of period	5,373,351	5,085,440	5,373,351	5,085,440
Arizona Public Service Company | AOCI Including Portion Attributable to Noncontrolling Interest
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(25,112)	(25,928)	(25,423)	(27,097)
Balance at end of period	(23,616)	(24,360)	(23,616)	(24,360)
Arizona Public Service Company | Accumulated Net Gain (Loss) from Cash Flow Hedges Including Portion Attributable to Noncontrolling Interest
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
OCI (loss) before reclassifications	9	(29)	(754)	(595)
Amounts reclassified from accumulated other comprehensive loss	710	798	2,480	2,564
Total other comprehensive income	719	769	1,726	1,969
Arizona Public Service Company | Accumulated Defined Benefit Plans Adjustment Including Portion Attributable to Noncontrolling Interest
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
OCI (loss) before reclassifications	0	0	(2,121)	(1,521)
Amounts reclassified from accumulated other comprehensive loss	777	799	2,202	2,289
Total other comprehensive income	$ 777	$ 799	$ 81	$ 768