Income Taxes - Components of Deferred Income Tax Liability (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
DEFERRED TAX ASSETS
Risk management activities	$ 26,614	$ 70,498
Regulatory liabilities:
Asset retirement obligation and removal costs	200,140	216,765
Unamortized investment tax credits	113,195	100,779
Other postretirement liabilities	60,375	83,034
Other	63,311	60,707
Pension liabilities	204,436	191,028
Renewable energy incentives	56,379	60,956
Credit and loss carryforwards	75,944	59,557
Other	158,421	149,033
Total deferred tax assets	958,815	992,357
DEFERRED TAX LIABILITIES
Plant-related	(3,297,989)	(3,116,752)
Risk management activities	(7,594)	(10,626)
Other postretirement assets	(63,477)	(71,737)
Regulatory assets:
Allowance for equity funds used during construction	(61,088)	(54,110)
Deferred fuel and purchased power — mark-to-market	(21,396)	(55,020)
Pension benefits	(274,184)	(240,692)
Retired power plant costs (see Note 3)	(49,166)	(53,420)
Other	(123,987)	(108,441)
Other	(5,166)	(4,984)
Total deferred tax liabilities	(3,904,047)	(3,715,782)
Deferred income taxes — net	(2,945,232)	(2,723,425)
ARIZONA PUBLIC SERVICE COMPANY
DEFERRED TAX ASSETS
Risk management activities	26,614	70,498
Regulatory liabilities:
Asset retirement obligation and removal costs	200,140	216,765
Unamortized investment tax credits	113,195	100,779
Other postretirement liabilities	60,375	83,034
Other	63,311	60,707
Pension liabilities	194,981	181,787
Renewable energy incentives	56,379	60,956
Credit and loss carryforwards	1,645	0
Other	187,453	176,016
Total deferred tax assets	904,093	950,542
DEFERRED TAX LIABILITIES
Plant-related	(3,297,989)	(3,116,752)
Risk management activities	(7,594)	(10,626)
Other postretirement assets	(62,819)	(70,986)
Regulatory assets:
Allowance for equity funds used during construction	(61,088)	(54,110)
Deferred fuel and purchased power — mark-to-market	(21,396)	(55,020)
Pension benefits	(274,184)	(240,692)
Retired power plant costs (see Note 3)	(49,166)	(53,420)
Other	(123,987)	(108,441)
Other	(5,165)	(4,984)
Total deferred tax liabilities	(3,903,388)	(3,715,031)
Deferred income taxes — net	$ (2,999,295)	$ (2,764,489)