SCHEDULE I - CONDENSED FINANCIAL INFORMATION OF REGISTRANT - Consolidated Statements of Cash Flows (Details) - USD ($)		3 Months Ended								12 Months Ended
	Nov. 30, 2017	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
Cash Flows from Operating Activities
Net income		$ 26,502,000	$ 280,945,000	$ 172,317,000	$ 28,185,000	$ 58,119,000	$ 267,900,000	$ 126,182,000	$ 9,326,000	$ 507,949,000	$ 461,527,000	$ 456,190,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization										610,629,000	565,011,000	571,664,000
Deferred income taxes										248,164,000	206,870,000	236,819,000
Accounts receivable										(93,797,000)	(2,489,000)	(22,219,000)
Accounts payable										(23,769,000)	(66,917,000)	(34,266,000)
Net cash flow provided by operating activities										1,118,036,000	1,023,390,000	1,094,327,000
Cash flows from investing activities
Net cash flow used for investing activities										(1,428,537,000)	(1,252,078,000)	(1,066,233,000)
Cash flows from financing activities
Issuance of long-term debt										848,239,000	693,151,000	842,415,000
Short-term debt borrowings under revolving credit facility										58,000,000	40,000,000	0
Short-term debt repayments under revolving credit facility										(32,000,000)	0	0
Dividends paid on common stock										(289,793,000)	(274,229,000)	(260,027,000)
Repayment of long-term debt										(125,000,000)	(370,430,000)	(415,570,000)
Common stock equity issuance and purchases - net										(13,390,000)	(4,867,000)	19,373,000
Net cash flow provided by financing activities										315,512,000	198,081,000	3,790,000
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS										5,011,000	(30,607,000)	31,884,000
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR					8,881,000				39,488,000	8,881,000	39,488,000	7,604,000
CASH AND CASH EQUIVALENTS AT END OF YEAR		13,892,000				8,881,000				13,892,000	8,881,000	39,488,000
Pinnacle West
Cash Flows from Operating Activities
Net income										488,456,000	442,034,000	437,257,000
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in earnings of subsidiaries - net										(507,495,000)	(462,027,000)	(446,508,000)
Depreciation and amortization										76,000	85,000	92,000
Deferred income taxes										(264,000)	(12,402,000)	12,967,000
Accounts receivable										(2,106,000)	15,823,000	11,336,000
Accounts payable										(11,162,000)	10,402,000	637,000
Accrued taxes and income tax receivable - net										(22,247,000)	20,041,000	(12,882,000)
Dividends received from subsidiaries										296,800,000	239,300,000	266,900,000
Other										15,092,000	5,514,000	(6,995,000)
Net cash flow provided by operating activities										257,150,000	258,770,000	262,804,000
Cash flows from investing activities
Construction work in progress										0	(18,457,000)	(3,462,000)
Investments in subsidiaries	$ (150,000,000)									(178,027,000)	(19,242,000)	(3,491,000)
Repayments of loans from subsidiaries										2,987,000	1,026,000	157,000
Advances of loans to subsidiaries										(6,388,000)	(2,092,000)	(1,010,000)
Net cash flow used for investing activities										(181,428,000)	(38,765,000)	(7,806,000)
Cash flows from financing activities
Issuance of long-term debt										298,761,000	0	0
Short-term debt borrowings under revolving credit facility										58,000,000	40,000,000	0
Short-term debt repayments under revolving credit facility										(32,000,000)	0	0
Commercial Paper - net										27,700,000	1,700,000	0
Dividends paid on common stock										(289,793,000)	(274,229,000)	(260,027,000)
Repayment of long-term debt										(125,000,000)	0	0
Common stock equity issuance and purchases - net										(13,390,000)	(4,867,000)	19,373,000
Net cash flow provided by financing activities										(75,722,000)	(237,396,000)	(240,654,000)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS										0	(17,391,000)	14,344,000
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR					$ 41,000				$ 17,432,000	41,000	17,432,000	3,088,000
CASH AND CASH EQUIVALENTS AT END OF YEAR		$ 41,000				$ 41,000				$ 41,000	$ 41,000	$ 17,432,000