Nuclear Decommissioning Trusts (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Nuclear decommissioning trust fund assets
Fair Value	$ 767,416		$ 767,416		$ 735,196
Realized gains and losses and proceeds from the sale of securities by the nuclear decommissioning trust funds
Proceeds from the sale of securities			290,594	$ 225,779
Fair value of fixed income securities, summarized by contractual maturities
Total	767,416		767,416		735,196
Arizona Public Service Company
Nuclear decommissioning trust fund assets
Fair Value	767,416		767,416		735,196
Unrealized Gains	188,879		188,879		169,053
Unrealized Losses	(352)		(352)		(2,760)
Net payables for securities purchases	(13,139)		(13,139)		(335)
Realized gains and losses and proceeds from the sale of securities by the nuclear decommissioning trust funds
Realized gains	2,282	$ 1,260	4,720	2,455
Realized losses	(1,350)	(1,525)	(3,136)	(2,050)
Proceeds from the sale of securities	148,785	$ 110,498	290,594	$ 225,779
Fair value of fixed income securities, summarized by contractual maturities
Total	767,416		767,416		735,196
Arizona Public Service Company | Equity Securities
Nuclear decommissioning trust fund assets
Fair Value	328,037		328,037		314,957
Unrealized Gains	165,926		165,926		157,098
Unrealized Losses	(7)		(7)		(115)
Fair value of fixed income securities, summarized by contractual maturities
Total	328,037		328,037		314,957
Arizona Public Service Company | Fixed income securities.
Nuclear decommissioning trust fund assets
Fair Value	452,518		452,518		420,574
Unrealized Gains	22,953		22,953		11,955
Unrealized Losses	(345)		(345)		(2,645)
Fair value of fixed income securities, summarized by contractual maturities
Less than one year	13,046		13,046
1 year - 5 years	133,548		133,548
5 years - 10 years	103,874		103,874
Greater than 10 years	202,050		202,050
Total	$ 452,518		$ 452,518		$ 420,574