Nuclear Decommissioning Trusts (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Nuclear decommissioning trust fund assets
Fair Value	$ 805,048		$ 779,586
Realized gains and losses and proceeds from the sale of securities by the nuclear decommissioning trust funds
Proceeds from the sale of securities	151,126	$ 141,809
Fair value of fixed income securities, summarized by contractual maturities
Total	805,048		779,586
Arizona Public Service Company
Nuclear decommissioning trust fund assets
Fair Value	805,048		779,586
Unrealized Gains	217,730		197,911
Unrealized Losses	(3,963)		(4,962)
Net receivables for securities purchases	337		795
Realized gains and losses and proceeds from the sale of securities by the nuclear decommissioning trust funds
Realized gains	2,367	2,438
Realized losses	(2,453)	(1,786)
Proceeds from the sale of securities	151,126	$ 141,809
Fair value of fixed income securities, summarized by contractual maturities
Total	805,048		779,586
Arizona Public Service Company | Equity Securities
Nuclear decommissioning trust fund assets
Fair Value	374,695		353,261
Unrealized Gains	207,708		188,091
Unrealized Losses	0		0
Fair value of fixed income securities, summarized by contractual maturities
Total	374,695		353,261
Arizona Public Service Company | Fixed income securities.
Nuclear decommissioning trust fund assets
Fair Value	430,016		425,530
Unrealized Gains	10,022		9,820
Unrealized Losses	(3,963)		(4,962)
Fair value of fixed income securities, summarized by contractual maturities
Less than one year	12,143
1 year – 5 years	117,217
5 years – 10 years	114,131
Greater than 10 years	186,525
Total	$ 430,016		$ 425,530