Nuclear Decommissioning Trusts (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Nuclear decommissioning trust fund assets
Fair Value	$ 841,980		$ 841,980		$ 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			351,860	$ 447,419
Fair value of fixed income securities, summarized by contractual maturities
Total	841,980		841,980		779,586
Arizona Public Service Company
Nuclear decommissioning trust fund assets
Fair Value	841,980		841,980		779,586
Unrealized Gains	244,999		244,999		197,911
Unrealized Losses	(2,177)		(2,177)		(4,962)
Net receivables for securities purchases	4,378		4,378		795
Realized gains and losses and proceeds from the sale of securities by the nuclear decommissioning trust funds
Realized gains	598	$ 4,033	3,904	8,753
Realized losses	(1,022)	(3,345)	(4,634)	(6,481)
Proceeds from the sale of securities	76,496	$ 156,825	351,860	$ 447,419
Fair value of fixed income securities, summarized by contractual maturities
Total	841,980		841,980		779,586
Arizona Public Service Company | Equity Securities
Nuclear decommissioning trust fund assets
Fair Value	401,913		401,913		353,261
Unrealized Gains	232,727		232,727		188,091
Unrealized Losses	0		0		0
Fair value of fixed income securities, summarized by contractual maturities
Total	401,913		401,913		353,261
Arizona Public Service Company | Fixed income securities.
Nuclear decommissioning trust fund assets
Fair Value	435,689		435,689		425,530
Unrealized Gains	12,272		12,272		9,820
Unrealized Losses	(2,177)		(2,177)		(4,962)
Fair value of fixed income securities, summarized by contractual maturities
Less than one year	22,498		22,498
1 year – 5 years	103,033		103,033
5 years – 10 years	117,044		117,044
Greater than 10 years	193,114		193,114
Total	$ 435,689		$ 435,689		$ 425,530