Retirement Plans and Other Postretirement Benefits - Schedule of Fair Value of Pinnacle West's Pension Plan (Details) - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Pension Plans
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Other	$ 451,472	$ 432,742
Fair value of plan assets	2,670,521	2,639,862	$ 2,835,549
Pension Plans | 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	798,403	748,033
Pension Plans | 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	1,420,646	1,459,087
Other Benefits Plans
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Other	193,845	165,813
Fair value of plan assets	767,316	702,192	$ 696,494
Other Benefits Plans | 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	362,005	337,359
Other Benefits Plans | 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	211,466	199,020
Cash and cash equivalents | Pension Plans
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	1,756	9,055
Cash and cash equivalents | Pension Plans | 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	1,756	9,055
Cash and cash equivalents | Pension Plans | 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 Plans
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	475	840
Cash and cash equivalents | Other Benefits Plans | 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	475	840
Cash and cash equivalents | Other Benefits Plans | 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 Plans
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	1,300,163	1,325,833
Corporate | Pension Plans | 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 Plans | 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	1,300,163	1,325,833
Corporate | Other Benefits Plans
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	200,469	186,435
Corporate | Other Benefits Plans | 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 Plans | 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	200,469	186,435
U.S. Treasury | Pension Plans
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	607,621	561,317
U.S. Treasury | Pension Plans | 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	607,621	561,317
U.S. Treasury | Pension Plans | 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 Plans
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	165,294	204,274
U.S. Treasury | Other Benefits Plans | 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	165,294	204,274
U.S. Treasury | Other Benefits Plans | 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 | Pension Plans
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	120,483	133,254
Other | Pension Plans | 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 | Pension Plans | 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	120,483	133,254
Other | Other Benefits Plans
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	10,997	12,585
Other | Other Benefits Plans | 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 | Other Benefits Plans | 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	10,997	12,585
Common stock equities | Pension Plans
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	73,548	74,939
Common stock equities | Pension Plans | 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	73,548	74,939
Common stock equities | Pension Plans | 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 Plans
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	98,296	89,685
Common stock equities | Other Benefits Plans | 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	98,296	89,685
Common stock equities | Other Benefits Plans | 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 Plans
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	115,478	102,722
Mutual funds | Pension Plans | 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	115,478	102,722
Mutual funds | Pension Plans | 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 Plans
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	27,986	23,415
Mutual funds | Other Benefits Plans | 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	27,986	23,415
Mutual funds | Other Benefits Plans | 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 Plans
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Other	266,624	244,734
Fair value of plan assets	266,624	244,734
Equities | Pension Plans | 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 Plans | 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 Plans
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Other	167,103	140,178
Fair value of plan assets	167,103	140,178
Equities | Other Benefits Plans | 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 Plans | 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 Plans
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Other	114,782	127,397
Fair value of plan assets	114,782	127,397
Real estate | Pension Plans | 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 Plans | 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 Plans
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Other	20,228	19,474
Fair value of plan assets	20,228	19,474
Real estate | Other Benefits Plans | 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 Plans | 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 | Pension Plans
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Other	70,066	60,611
Fair value of plan assets	70,066	60,611
Other | Pension Plans | 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 | Pension Plans | 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 | Other Benefits Plans
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Other	6,514	6,161
Fair value of plan assets	76,468	25,306
Other | Other Benefits Plans | 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	69,954	19,145
Other | Other Benefits Plans | 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