Income Taxes - Components of Income Tax Expense (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current:
Federal									$ 11,624	$ 8,630	$ (12,335)
State									3,052	1,259	4,763
Total current									14,676	9,889	(7,572)
Deferred:
Federal									223,729	201,743	221,505
State									19,867	24,779	23,787
Total deferred									243,596	226,522	245,292
Income tax expense	$ 20,775	$ 144,319	$ 88,967	$ 4,211	$ 27,309	$ 141,446	$ 65,742	$ 1,914	258,272	236,411	237,720
ARIZONA PUBLIC SERVICE COMPANY
Current:
Federal									21,512	711	6,485
State									2,778	4,276	7,813
Total current									24,290	4,987	14,298
Deferred:
Federal									221,078	215,178	208,326
State									23,800	25,677	23,217
Total deferred									244,878	240,855	231,543
Income tax expense									$ 269,168	$ 245,842	$ 245,841