Income Taxes - Components of Deferred Income Tax Liability (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
DEFERRED TAX ASSETS
Risk management activities	$ 70,498	$ 57,505
Regulatory liabilities:
Asset retirement obligation and removal costs	216,765	229,772
Unamortized investment tax credits	100,779	96,232
Other postretirement liabilities	83,034	90,496
Other	60,707	60,409
Pension liabilities	191,028	205,227
Renewable energy incentives	60,956	65,169
Credit and loss carryforwards	59,557	68,347
Other	149,033	138,729
Total deferred tax assets	992,357	1,011,886
DEFERRED TAX LIABILITIES
Plant-related	(3,116,752)	(2,958,369)
Risk management activities	(10,626)	(12,171)
Other postretirement assets	(71,737)	(59,170)
Regulatory assets:
Allowance for equity funds used during construction	(54,110)	(48,286)
Deferred fuel and purchased power	0	(2,498)
Deferred fuel and purchased power — mark-to-market	(55,020)	(38,187)
Pension benefits	(240,692)	(191,747)
Retired power plant costs (see Note 3)	(53,420)	(57,255)
Other	(108,441)	(99,123)
Other	(4,984)	(5,484)
Total deferred tax liabilities	3,715,782	3,472,290
Deferred income taxes — net	(2,723,425)	(2,460,404)
ARIZONA PUBLIC SERVICE COMPANY
DEFERRED TAX ASSETS
Risk management activities	70,498	57,505
Regulatory liabilities:
Asset retirement obligation and removal costs	216,765	229,772
Unamortized investment tax credits	100,779	96,232
Other postretirement liabilities	83,034	90,496
Other	60,707	60,409
Pension liabilities	181,787	194,541
Renewable energy incentives	60,956	65,169
Credit and loss carryforwards	0	0
Other	176,016	161,379
Total deferred tax assets	950,542	955,503
DEFERRED TAX LIABILITIES
Plant-related	(3,116,752)	(2,958,369)
Risk management activities	(10,626)	(12,171)
Other postretirement assets	(70,986)	(58,495)
Regulatory assets:
Allowance for equity funds used during construction	(54,110)	(48,286)
Deferred fuel and purchased power	0	(2,498)
Deferred fuel and purchased power — mark-to-market	(55,020)	(38,187)
Pension benefits	(240,692)	(191,747)
Retired power plant costs (see Note 3)	(53,420)	(57,255)
Other	(108,441)	(99,123)
Other	(4,984)	(5,484)
Total deferred tax liabilities	3,715,031	3,471,615
Deferred income taxes — net	$ (2,764,489)	$ (2,516,112)