SCHEDULE I - CONDENSED FINANCIAL INFORMATION OF REGISTRANT - Statement of Comprehensive Income (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
CONDENSED FINANCIAL STATEMENTS
Operating revenues	$ 759,659	$ 1,183,322	$ 944,587	$ 677,728	$ 739,199	$ 1,166,922	$ 915,394	$ 677,167	$ 3,565,296	$ 3,498,682	$ 3,495,443
Operating expenses									2,630,869	2,642,698	2,640,841
OPERATING INCOME	90,610	466,082	304,229	73,506	122,816	451,258	231,748	50,162	934,427	855,984	854,602
Other
Total									29,478	27,704	18,013
Interest expense									219,796	205,720	194,964
Income tax benefit	20,775	144,319	88,967	4,211	27,309	141,446	65,742	1,914	258,272	236,411	237,720
NET INCOME ATTRIBUTABLE TO COMMON SHAREHOLDERS	$ 21,629	$ 276,072	$ 167,443	$ 23,312	$ 53,246	$ 263,027	$ 121,308	$ 4,453	488,456	442,034	437,257
Other comprehensive income									(1,180)	926	23,393
COMPREHENSIVE INCOME ATTRIBUTABLE TO COMMON SHAREHOLDERS									487,276	442,960	460,650
Pinnacle West
CONDENSED FINANCIAL STATEMENTS
Operating revenues									119	370	550
Operating expenses									24,298	26,424	12,733
OPERATING INCOME									(24,179)	(26,054)	(12,183)
Other
Equity in earnings of subsidiaries									507,495	462,027	446,508
Other expense									(2,715)	(1,771)	(3,302)
Total									504,780	460,256	443,206
Interest expense									5,633	3,151	2,672
INCOME BEFORE INCOME TAXES									474,968	431,051	428,351
Income tax benefit									(13,488)	(10,983)	(8,906)
NET INCOME ATTRIBUTABLE TO COMMON SHAREHOLDERS									488,456	442,034	437,257
Other comprehensive income									(1,180)	926	23,393
COMPREHENSIVE INCOME ATTRIBUTABLE TO COMMON SHAREHOLDERS									$ 487,276	$ 442,960	$ 460,650