Nuclear Decommissioning Trusts (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Nuclear decommissioning trust fund assets
Fair Value	$ 822,244		$ 822,244		$ 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			275,364	$ 290,594
Fair value of fixed income securities, summarized by contractual maturities
Total	822,244		822,244		779,586
Arizona Public Service Company
Nuclear decommissioning trust fund assets
Fair Value	822,244		822,244		779,586
Unrealized Gains	229,512		229,512		197,911
Unrealized Losses	(2,630)		(2,630)		(4,962)
Net receivables for securities purchases	1,833		1,833		795
Realized gains and losses and proceeds from the sale of securities by the nuclear decommissioning trust funds
Realized gains	939	$ 2,282	3,306	4,720
Realized losses	(1,159)	(1,350)	(3,612)	(3,136)
Proceeds from the sale of securities	124,238	$ 148,785	275,364	$ 290,594
Fair value of fixed income securities, summarized by contractual maturities
Total	822,244		822,244		779,586
Arizona Public Service Company | Equity Securities
Nuclear decommissioning trust fund assets
Fair Value	384,999		384,999		353,261
Unrealized Gains	217,288		217,288		188,091
Unrealized Losses	0		0		0
Fair value of fixed income securities, summarized by contractual maturities
Total	384,999		384,999		353,261
Arizona Public Service Company | Fixed income securities.
Nuclear decommissioning trust fund assets
Fair Value	435,412		435,412		425,530
Unrealized Gains	12,224		12,224		9,820
Unrealized Losses	(2,630)		(2,630)		(4,962)
Fair value of fixed income securities, summarized by contractual maturities
Less than one year	14,979		14,979
1 year – 5 years	123,392		123,392
5 years – 10 years	107,622		107,622
Greater than 10 years	189,419		189,419
Total	$ 435,412		$ 435,412		$ 425,530