SCHEDULE I - CONDENSED FINANCIAL INFORMATION OF REGISTRANT - Consolidated Balance Sheets (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Current assets
Cash and cash equivalents	$ 13,892,000	$ 8,881,000	$ 39,488,000	$ 7,604,000
Accounts receivable	305,147,000	250,491,000
Income tax receivable	0	3,751,000
Other current assets	48,039,000	45,028,000
Total current assets	1,016,288,000	822,219,000
Investments and other assets
Other assets	84,531,000	69,063,000
Total investments and other assets	955,582,000	848,650,000
Total Assets	17,019,082,000	16,004,253,000
Current liabilities
Accounts payable	256,442,000	264,631,000
Accrued taxes	148,946,000	138,964,000
Common dividends payable	77,667,000	72,926,000
Short-term borrowings	95,400,000	177,200,000
Current maturities of long-term debt	82,000,000	125,000,000
Other current liabilities	246,529,000	244,000,000
Total current liabilities	1,197,852,000	1,292,946,000
Deferred credits and other
Long-term debt less current maturities	4,789,713,000	4,021,785,000
Other	148,909,000	156,784,000
Total deferred credits and other	5,895,787,000	5,753,610,000
Common stock equity
Common stock	2,614,805,000	2,596,030,000
Accumulated other comprehensive loss	(45,002,000)	(43,822,000)
Retained earnings	2,442,511,000	2,255,547,000
Total shareholders’ equity	5,006,690,000	4,803,622,000
Noncontrolling interests	129,040,000	132,290,000
Total equity	5,135,730,000	4,935,912,000	4,719,457,000	4,519,102,000
Total Liabilities and Equity	17,019,082,000	16,004,253,000
Pinnacle West
Current assets
Cash and cash equivalents	41,000	41,000	$ 17,432,000	$ 3,088,000
Accounts receivable	93,554,000	81,751,000
Income tax receivable	19,124,000	0
Other current assets	267,000	340,000
Total current assets	112,986,000	82,132,000
Investments and other assets
Investments in subsidiaries	5,465,137,000	5,084,035,000
Deferred income taxes	54,352,000	53,805,000
Other assets	44,613,000	38,500,000
Total investments and other assets	5,564,102,000	5,176,340,000
Total Assets	5,677,088,000	5,258,472,000
Current liabilities
Accounts payable	7,638,000	5,421,000
Accrued taxes	8,927,000	12,050,000
Common dividends payable	77,667,000	72,926,000
Short-term borrowings	95,400,000	41,700,000
Current maturities of long-term debt	0	125,000,000
Other current liabilities	17,417,000	31,182,000
Total current liabilities	207,049,000	288,279,000
Deferred credits and other
Long-term debt less current maturities	298,421,000	0
Pension liabilities	20,758,000	21,057,000
Other	15,130,000	13,224,000
Total deferred credits and other	35,888,000	34,281,000
Common stock equity
Common stock	2,609,181,000	2,591,897,000
Accumulated other comprehensive loss	(45,002,000)	(43,822,000)
Retained earnings	2,442,511,000	2,255,547,000
Total shareholders’ equity	5,006,690,000	4,803,622,000
Noncontrolling interests	129,040,000	132,290,000
Total equity	5,135,730,000	4,935,912,000
Total Liabilities and Equity	$ 5,677,088,000	$ 5,258,472,000