SCHEDULE I - CONDENSED FINANCIAL INFORMATION OF REGISTRANT - Balance Sheets (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current assets
Cash and cash equivalents	$ 5,766	$ 13,892	$ 8,881	$ 39,488
Accounts receivable	267,887	305,147
Other current assets	56,128	48,039
Total current assets	924,991	1,016,288
Investments and other assets
Other assets	103,247	52,040
Total investments and other assets	1,190,482	955,582
Total Assets	17,664,202	17,019,082
Current liabilities
Accounts payable	277,336	256,442
Accrued taxes	154,819	148,946
Common dividends payable	82,675	77,667
Short-term borrowings	76,400	95,400
Other current liabilities	184,229	246,529
Total current liabilities	1,648,964	1,197,852
Deferred credits and other
Long-term debt less current maturities (Note 6)	4,638,232	4,789,713
Other	147,640	148,909
Total deferred credits and other	6,028,301	5,895,787
COMMITMENTS AND CONTINGENCIES (SEE NOTES)
Common stock equity
Common stock	2,634,265	2,614,805
Accumulated other comprehensive loss	(47,708)	(45,002)
Retained earnings	2,641,183	2,442,511
Total shareholders’ equity	5,222,915	5,006,690
Noncontrolling interests	125,790	129,040
Total equity	5,348,705	5,135,730	4,935,912	4,719,457
Total Liabilities and Equity	17,664,202	17,019,082
Pinnacle West
Current assets
Cash and cash equivalents	41	41	$ 41	$ 17,432
Accounts receivable	99,989	93,554
Income tax receivable	32,737	19,124
Other current assets	1,502	267
Total current assets	134,269	112,986
Investments and other assets
Investments in subsidiaries	5,859,834	5,465,137
Deferred income taxes	5,243	54,352
Other assets	34,910	44,613
Total investments and other assets	5,899,987	5,564,102
Total Assets	6,034,256	5,677,088
Current liabilities
Accounts payable	9,565	7,638
Accrued taxes	9,006	8,927
Common dividends payable	82,675	77,667
Short-term borrowings	76,400	95,400
Other current liabilities	19,215	17,417
Total current liabilities	196,861	207,049
Deferred credits and other
Long-term debt less current maturities (Note 6)	448,796	298,421
Pension liabilities	17,766	20,758
Other	22,128	15,130
Total deferred credits and other	39,894	35,888
COMMITMENTS AND CONTINGENCIES (SEE NOTES)
Common stock equity
Common stock	2,629,440	2,609,181
Accumulated other comprehensive loss	(47,708)	(45,002)
Retained earnings	2,641,183	2,442,511
Total shareholders’ equity	5,222,915	5,006,690
Noncontrolling interests	125,790	129,040
Total equity	5,348,705	5,135,730
Total Liabilities and Equity	$ 6,034,256	$ 5,677,088