Nuclear Decommissioning Trusts (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Nuclear decommissioning trust fund assets
Fair Value	$ 751,954		$ 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	141,809	$ 115,282
Fair value of fixed income securities, summarized by contractual maturities
Total	751,954		735,196
Arizona Public Service Company
Nuclear decommissioning trust fund assets
Fair Value	751,954		735,196
Unrealized Gains	178,040		169,053
Unrealized Losses	(741)		(2,760)
Net payables for securities purchases	(1,898)		(335)
Realized gains and losses and proceeds from the sale of securities by the nuclear decommissioning trust funds
Realized gains	2,438	1,195
Realized losses	(1,786)	(525)
Proceeds from the sale of securities	141,809	$ 115,282
Fair value of fixed income securities, summarized by contractual maturities
Total	751,954		735,196
Arizona Public Service Company | Equity Securities
Nuclear decommissioning trust fund assets
Fair Value	319,971		314,957
Unrealized Gains	159,790		157,098
Unrealized Losses	(65)		(115)
Fair value of fixed income securities, summarized by contractual maturities
Total	319,971		314,957
Arizona Public Service Company | Fixed income securities.
Nuclear decommissioning trust fund assets
Fair Value	433,881		420,574
Unrealized Gains	18,250		11,955
Unrealized Losses	(676)		(2,645)
Fair value of fixed income securities, summarized by contractual maturities
Less than one year	11,633
1 year - 5 years	126,221
5 years - 10 years	101,773
Greater than 10 years	194,254
Total	$ 433,881		$ 420,574