Retirement Plans and Other Postretirement Benefits - Fair Value of Pinnacle West's Pension Plan (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Pension Benefits
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Other	$ 530,171	$ 691,233
Fair value of plan assets	3,812,041	3,886,544	$ 3,318,351
Pension Benefits | Level 1
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Gross fair value of plan assets	1,350,751	1,398,305
Pension Benefits | Level 2
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Gross fair value of plan assets	1,931,119	1,797,006
Other Benefits
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Other	126,552	118,440
Fair value of plan assets	872,435	961,165	$ 837,494
Other Benefits | Level 1
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Gross fair value of plan assets	491,981	612,921
Other Benefits | Level 2
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Gross fair value of plan assets	253,902	229,804
Cash and cash equivalents | Pension Benefits
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Other	0	0
Fair value of plan assets	821	9,911
Cash and cash equivalents | Pension Benefits | Level 1
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Gross fair value of plan assets	821	9,911
Cash and cash equivalents | Pension Benefits | Level 2
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Gross fair value of plan assets	0	0
Cash and cash equivalents | Other Benefits
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Other	0	0
Fair value of plan assets	121	1,909
Cash and cash equivalents | Other Benefits | Level 1
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Gross fair value of plan assets	121	1,909
Cash and cash equivalents | Other Benefits | Level 2
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Gross fair value of plan assets	0	0
Corporate | Pension Benefits
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Other	0	0
Fair value of plan assets	1,765,623	1,684,782
Corporate | Pension Benefits | Level 1
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Gross fair value of plan assets	0	0
Corporate | Pension Benefits | Level 2
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Gross fair value of plan assets	1,765,623	1,684,782
Corporate | Other Benefits
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Other	0	0
Fair value of plan assets	244,572	221,488
Corporate | Other Benefits | Level 1
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Gross fair value of plan assets	0	0
Corporate | Other Benefits | Level 2
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Gross fair value of plan assets	244,572	221,488
U.S. Treasury | Pension Benefits
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Other	0	0
Fair value of plan assets	1,008,211	794,571
U.S. Treasury | Pension Benefits | Level 1
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Gross fair value of plan assets	1,008,211	794,571
U.S. Treasury | Pension Benefits | Level 2
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Gross fair value of plan assets	0	0
U.S. Treasury | Other Benefits
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Other	0	0
Fair value of plan assets	287,057	258,102
U.S. Treasury | Other Benefits | Level 1
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Gross fair value of plan assets	287,057	258,102
U.S. Treasury | Other Benefits | Level 2
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Gross fair value of plan assets	0	0
Other fixed income | Pension Benefits
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Other	0	0
Fair value of plan assets	165,496	112,224
Other fixed income | Pension Benefits | Level 1
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Gross fair value of plan assets	0	0
Other fixed income | Pension Benefits | Level 2
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Gross fair value of plan assets	165,496	112,224
Other fixed income | Other Benefits
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Other	0	0
Fair value of plan assets	9,330	8,316
Other fixed income | Other Benefits | Level 1
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Gross fair value of plan assets	0	0
Other fixed income | Other Benefits | Level 2
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Gross fair value of plan assets	9,330	8,316
Common stock equities | Pension Benefits
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Other	0	0
Fair value of plan assets	209,063	331,058
Common stock equities | Pension Benefits | Level 1
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Gross fair value of plan assets	209,063	331,058
Common stock equities | Pension Benefits | Level 2
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Gross fair value of plan assets	0	0
Common stock equities | Other Benefits
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Other	0	0
Fair value of plan assets	176,024	175,605
Common stock equities | Other Benefits | Level 1
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Gross fair value of plan assets	176,024	175,605
Common stock equities | Other Benefits | Level 2
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Gross fair value of plan assets	0	0
Mutual funds | Pension Benefits
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Other	0	0
Fair value of plan assets	132,656	262,765
Mutual funds | Pension Benefits | Level 1
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Gross fair value of plan assets	132,656	262,765
Mutual funds | Pension Benefits | Level 2
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Gross fair value of plan assets	0	0
Mutual funds | Other Benefits
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Other	0	0
Fair value of plan assets	26,262	34,310
Mutual funds | Other Benefits | Level 1
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Gross fair value of plan assets	26,262	34,310
Mutual funds | Other Benefits | Level 2
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Gross fair value of plan assets	0	0
Equities | Pension Benefits
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Other	255,141	407,522
Fair value of plan assets	255,141	407,522
Equities | Pension Benefits | Level 1
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Gross fair value of plan assets	0	0
Equities | Pension Benefits | Level 2
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Gross fair value of plan assets	0	0
Equities | Other Benefits
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Other	96,547	94,674
Fair value of plan assets	96,547	94,674
Equities | Other Benefits | Level 1
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Gross fair value of plan assets	0	0
Equities | Other Benefits | Level 2
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Gross fair value of plan assets	0	0
Real estate | Pension Benefits
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Other	173,197	191,595
Fair value of plan assets	173,197	191,595
Real estate | Pension Benefits | Level 1
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Gross fair value of plan assets	0	0
Real estate | Pension Benefits | Level 2
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Gross fair value of plan assets	0	0
Real estate | Other Benefits
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Other	23,851	19,778
Fair value of plan assets	23,851	19,778
Real estate | Other Benefits | Level 1
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Gross fair value of plan assets	0	0
Real estate | Other Benefits | Level 2
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Gross fair value of plan assets	0	0
Partnerships | Pension Benefits
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Other	15,730	22,420
Fair value of plan assets	15,730	22,420
Partnerships | Pension Benefits | Level 1
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Gross fair value of plan assets	0	0
Partnerships | Pension Benefits | Level 2
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Gross fair value of plan assets	0	0
Short-term investments and other | Pension Benefits
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Other	86,103	69,696
Fair value of plan assets	86,103	69,696
Short-term investments and other | Pension Benefits | Level 1
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Gross fair value of plan assets	0	0
Short-term investments and other | Pension Benefits | Level 2
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Gross fair value of plan assets	0	0
Short-term investments and other | Other Benefits
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Other	6,154	3,988
Fair value of plan assets	8,671	146,983
Short-term investments and other | Other Benefits | Level 1
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Gross fair value of plan assets	2,517	142,995
Short-term investments and other | Other Benefits | Level 2
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Gross fair value of plan assets	$ 0	$ 0