Nuclear Decommissioning Trusts (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Nuclear decommissioning trust fund assets
Fair Value	$ 779,753		$ 779,753		$ 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			447,419	$ 330,304
Fair value of fixed income securities, summarized by contractual maturities
Total	779,753		779,753		735,196
Arizona Public Service Company
Nuclear decommissioning trust fund assets
Fair Value	779,753		779,753		735,196
Unrealized Gains	197,299		197,299		169,053
Unrealized Losses	(468)		(468)		(2,760)
Net receivables for securities purchases	5,032		5,032
Net payables for securities purchases					(335)
Realized gains and losses and proceeds from the sale of securities by the nuclear decommissioning trust funds
Realized gains	4,033	$ 1,919	8,753	4,374
Realized losses	(3,345)	(2,106)	(6,481)	(4,156)
Proceeds from the sale of securities	156,825	$ 104,525	447,419	$ 330,304
Fair value of fixed income securities, summarized by contractual maturities
Total	779,753		779,753		735,196
Arizona Public Service Company | Equity Securities
Nuclear decommissioning trust fund assets
Fair Value	340,436		340,436		314,957
Unrealized Gains	176,495		176,495		157,098
Unrealized Losses	(3)		(3)		(115)
Fair value of fixed income securities, summarized by contractual maturities
Total	340,436		340,436		314,957
Arizona Public Service Company | Fixed income securities.
Nuclear decommissioning trust fund assets
Fair Value	434,285		434,285		420,574
Unrealized Gains	20,804		20,804		11,955
Unrealized Losses	(465)		(465)		(2,645)
Fair value of fixed income securities, summarized by contractual maturities
Less than one year	8,429		8,429
1 year - 5 years	134,200		134,200
5 years - 10 years	102,835		102,835
Greater than 10 years	188,821		188,821
Total	$ 434,285		$ 434,285		$ 420,574