Regulatory Matters - Schedule of Regulatory Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Detail of regulatory assets
Regulatory assets, current	$ 135,000	$ 138,000
Regulatory assets, non-current	1,081,113	1,054,087
Pension benefits
Detail of regulatory assets
Regulatory assets, current	0	0
Regulatory assets, non-current	505,000	485,000
Income taxes — allowance for funds used during construction (AFUDC) equity
Detail of regulatory assets
Regulatory assets, current	5,000	5,000
Regulatory assets, non-current	122,000	118,000
Deferred fuel and purchased power — mark-to-market (Note 7)
Detail of regulatory assets
Regulatory assets, current	53,000	51,000
Regulatory assets, non-current	62,000	46,000
Transmission vegetation management
Detail of regulatory assets
Regulatory assets, current	9,000	9,000
Regulatory assets, non-current	0	5,000
Coal reclamation
Detail of regulatory assets
Regulatory assets, current	0	0
Regulatory assets, non-current	6,000	7,000
Palo Verde VIEs (Note 6)
Detail of regulatory assets
Regulatory assets, current	0	0
Regulatory assets, non-current	26,000	35,000
Deferred compensation
Detail of regulatory assets
Regulatory assets, current	0	0
Regulatory assets, non-current	36,000	34,000
Deferred fuel and purchased power
Detail of regulatory assets
Regulatory assets, current	0	7,000
Regulatory assets, non-current	0	0
Tax expense of Medicare subsidy
Detail of regulatory assets
Regulatory assets, current	2,000	2,000
Regulatory assets, non-current	13,000	14,000
Loss on reacquired debt
Detail of regulatory assets
Regulatory assets, current	1,000	1,000
Regulatory assets, non-current	16,000	16,000
Income taxes — investment tax credit basis adjustment
Detail of regulatory assets
Regulatory assets, current	2,000	2,000
Regulatory assets, non-current	46,000	46,000
Pension and other postretirement benefits deferral
Detail of regulatory assets
Regulatory assets, current	0	4,000
Regulatory assets, non-current	0	0
Four Corners cost deferral
Detail of regulatory assets
Regulatory assets, current	7,000	7,000
Regulatory assets, non-current	67,000	70,000
Lost fixed cost recovery
Detail of regulatory assets
Regulatory assets, current	45,000	38,000
Regulatory assets, non-current	0	0
Retired power plant costs
Detail of regulatory assets
Regulatory assets, current	10,000	10,000
Regulatory assets, non-current	131,000	136,000
Deferred property taxes
Detail of regulatory assets
Regulatory assets, current	0	0
Regulatory assets, non-current	40,000	30,000
Other
Detail of regulatory assets
Regulatory assets, current	1,000	2,000
Regulatory assets, non-current	11,000	12,000
Arizona Public Service Company
Detail of regulatory assets
Regulatory assets, non-current	$ 1,081,113	$ 1,054,087