SCHEDULE I - CONDENSED FINANCIAL INFORMATION OF REGISTRANT - Cash Flows (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash Flows from Operating Activities
Net income	$ 68,854	$ 317,149	$ 149,019	$ 22,791	$ 30,949	$ 319,885	$ 171,612	$ 8,094	$ 557,813	$ 530,540	$ 507,949
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization									664,140	650,955	610,629
Deferred income taxes									(1,479)	117,355	248,164
Accounts receivable									(12,789)	37,530	(93,797)
Accounts payable									50,641	(14,602)	(23,769)
Net cash flow provided by operating activities									956,726	1,277,144	1,118,036
Cash flows from investing activities
Net cash flow used for investing activities									(1,130,977)	(1,192,824)	(1,428,537)
Cash flows from financing activities
Issuance of long-term debt									1,092,188	445,245	848,239
Short-term debt borrowings under revolving credit facility									49,000	45,000	58,000
Short-term debt repayments under revolving credit facility									(65,000)	(57,000)	(32,000)
Dividends paid on common stock									(329,643)	(308,892)	(289,793)
Repayment of long-term debt									(600,000)	(182,000)	(125,000)
Common stock equity issuance and purchases - net									692	(5,055)	(13,390)
Net cash flow provided by (used for) financing activities									178,768	(92,446)	315,512
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS									4,517	(8,126)	5,011
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR				5,766				13,892	5,766	13,892	8,881
CASH AND CASH EQUIVALENTS AT END OF YEAR	10,283				5,766				10,283	5,766	13,892
Pinnacle West
Cash Flows from Operating Activities
Net income									538,320	511,047	488,456
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in earnings of subsidiaries - net									(562,946)	(569,249)	(507,495)
Depreciation and amortization									76	76	76
Deferred income taxes									(35,831)	49,535	(264)
Accounts receivable									182	(7,881)	(2,106)
Accounts payable									(2,129)	1,967	(11,162)
Accrued taxes and income tax receivable - net									16,400	(13,535)	(22,247)
Dividends received from subsidiaries									336,300	316,000	296,800
Other									(1,300)	31,807	15,092
Net cash flow provided by operating activities									289,072	319,767	257,150
Cash flows from investing activities
Investments in subsidiaries									1,557	(142,796)	(178,027)
Repayments of loans from subsidiaries									4,190	6,477	2,987
Advances of loans to subsidiaries									(4,165)	(500)	(6,388)
Net cash flow used for investing activities									1,582	(136,819)	(181,428)
Cash flows from financing activities
Issuance of long-term debt									0	150,000	298,761
Short-term debt borrowings under revolving credit facility									49,000	20,000	58,000
Short-term debt repayments under revolving credit facility									(65,000)	(32,000)	(32,000)
Commercial paper - net									54,275	(7,000)	27,700
Dividends paid on common stock									(329,643)	(308,892)	(289,793)
Repayment of long-term debt									0	0	(125,000)
Common stock equity issuance and purchases - net									692	(5,055)	(13,390)
Other									0	(1)	0
Net cash flow provided by (used for) financing activities									(290,676)	(182,948)	(75,722)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS									(22)	0	0
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR				$ 41				$ 41	41	41	41
CASH AND CASH EQUIVALENTS AT END OF YEAR	$ 19				$ 41				$ 19	$ 41	$ 41