SCHEDULE I - CONDENSED FINANCIAL INFORMATION OF REGISTRANT - Cash Flows (Details) - USD ($)		3 Months Ended								12 Months Ended
	Dec. 21, 2018	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash Flows from Operating Activities
Net income		$ 30,949,000	$ 319,885,000	$ 171,612,000	$ 8,094,000	$ 26,502,000	$ 280,945,000	$ 172,317,000	$ 28,185,000	$ 530,540,000	$ 507,949,000	$ 461,527,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization										650,955,000	610,629,000	565,011,000
Deferred income taxes										117,355,000	248,164,000	206,870,000
Accounts receivable										37,530,000	(93,797,000)	(2,489,000)
Accounts payable										(14,602,000)	(23,769,000)	(66,917,000)
Net cash flow provided by operating activities										1,277,144,000	1,118,036,000	1,023,390,000
Cash flows from investing activities
Net cash flow used for investing activities										(1,192,824,000)	(1,428,537,000)	(1,252,078,000)
Cash flows from financing activities
Issuance of long-term debt										445,245,000	848,239,000	693,151,000
Short-term debt borrowings under revolving credit facility										45,000,000	58,000,000	40,000,000
Short-term debt repayments under revolving credit facility										(57,000,000)	(32,000,000)	0
Dividends paid on common stock										(308,892,000)	(289,793,000)	(274,229,000)
Repayment of long-term debt										(182,000,000)	(125,000,000)	(370,430,000)
Common stock equity issuance and purchases - net										(5,055,000)	(13,390,000)	(4,867,000)
Net cash flow (used for) provided by financing activities										(92,446,000)	315,512,000	198,081,000
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS										(8,126,000)	5,011,000	(30,607,000)
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR					13,892,000				8,881,000	13,892,000	8,881,000	39,488,000
CASH AND CASH EQUIVALENTS AT END OF YEAR		5,766,000				13,892,000				5,766,000	13,892,000	8,881,000
Pinnacle West
Cash Flows from Operating Activities
Net income										511,047,000	488,456,000	442,034,000
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in earnings of subsidiaries - net										(569,249,000)	(507,495,000)	(462,027,000)
Depreciation and amortization										76,000	76,000	85,000
Deferred income taxes										49,535,000	(264,000)	(12,402,000)
Accounts receivable										(7,881,000)	(2,106,000)	15,823,000
Accounts payable										1,967,000	(11,162,000)	10,402,000
Accrued taxes and income tax receivable - net										(13,535,000)	(22,247,000)	20,041,000
Dividends received from subsidiaries										316,000,000	296,800,000	239,300,000
Other										31,807,000	15,092,000	5,514,000
Net cash flow provided by operating activities										319,767,000	257,150,000	258,770,000
Cash flows from investing activities
Construction work in progress										0	0	(18,457,000)
Investments in subsidiaries	$ (150,000,000)									(142,796,000)	(178,027,000)	(19,242,000)
Repayments of loans from subsidiaries										6,477,000	2,987,000	1,026,000
Advances of loans to subsidiaries										(500,000)	(6,388,000)	(2,092,000)
Net cash flow used for investing activities										(136,819,000)	(181,428,000)	(38,765,000)
Cash flows from financing activities
Issuance of long-term debt										150,000,000	298,761,000	0
Short-term debt borrowings under revolving credit facility										20,000,000	58,000,000	40,000,000
Short-term debt repayments under revolving credit facility										(32,000,000)	(32,000,000)	0
Commercial paper - net										(7,000,000)	27,700,000	1,700,000
Dividends paid on common stock										(308,892,000)	(289,793,000)	(274,229,000)
Repayment of long-term debt										0	(125,000,000)	0
Common stock equity issuance and purchases - net										(5,055,000)	(13,390,000)	(4,867,000)
Other										(1,000)	0	0
Net cash flow (used for) provided by financing activities										(182,948,000)	(75,722,000)	(237,396,000)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS										0	0	(17,391,000)
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR					$ 41,000				$ 41,000	41,000	41,000	17,432,000
CASH AND CASH EQUIVALENTS AT END OF YEAR		$ 41,000				$ 41,000				$ 41,000	$ 41,000	$ 41,000