Changes in Accumulated Other Comprehensive Loss (Tables)

9 Months Ended

Sep. 30, 2025

Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]

Schedule of Changes in Accumulated Other Comprehensive Loss Including Reclassification Adjustments, by Component

The following tables show the changes in Pinnacle West’s consolidated accumulated other comprehensive loss, including reclassification adjustments, net of tax, by component (dollars in thousands): 

	Pension and Other Postretirement Benefits			Derivative Instruments		Total
Three Months Ended September 30
Balance June 30, 2025	$	(31,216)		$	775	$	(30,441)
Other comprehensive loss before reclassifications	—			(128)		(128)
Amounts reclassified from accumulated other comprehensive loss	478		(a)	—		478
Balance September 30, 2025	$	(30,738)		$	647	$	(30,091)
Balance June 30, 2024	$	(34,505)		$	1,211	$	(33,294)
Other comprehensive loss before reclassifications	—			(33)		(33)
Amounts reclassified from accumulated other comprehensive loss	513		(a)	—		513
Balance September 30, 2024	$	(33,992)		$	1,178	$	(32,814)

(a)    These amounts primarily represent amortization of actuarial loss and are included in the computation of net periodic pension cost.  See Note 7

	Pension and Other Postretirement Benefits			Derivative Instruments		Total
Nine Months Ended September 30
Balance December 31, 2024	$	(31,661)		$	719	$	(30,942)
Other comprehensive loss before reclassifications	(503)			(72)		(575)
Amounts reclassified from accumulated other comprehensive loss	1,426		(a)	—		1,426
Balance September 30, 2025	$	(30,738)		$	647	$	(30,091)
Balance December 31, 2023	$	(34,754)		$	1,610	$	(33,144)
Other comprehensive loss before reclassifications	(779)			(432)		(1,211)
Amounts reclassified from accumulated other comprehensive loss	1,541		(a)	—		1,541
Balance September 30, 2024	$	(33,992)		$	1,178	$	(32,814)

(a)    These amounts primarily represent amortization of actuarial loss and are included in the computation of net periodic pension cost.  See Note 7.

The following tables show the changes in APS’s accumulated other comprehensive loss, including reclassification adjustments, net of tax, by component (dollars in thousands): 

	Pension and Other Postretirement Benefits
Three Months Ended September 30
Balance June 30, 2025	$	(13,846)
Other comprehensive loss before reclassifications	—
Amounts reclassified from accumulated other comprehensive loss	387		(a)
Balance September 30, 2025	$	(13,459)
Balance June 30, 2024	$	(17,036)
Other comprehensive loss before reclassifications	—
Amounts reclassified from accumulated other comprehensive loss	450		(a)
Balance September 30, 2024	$	(16,586)

(a) These amounts primarily represent amortization of actuarial loss and are included in the computation of net periodic pension cost.  See Note 7.

	Pension and Other Postretirement Benefits
Nine Months Ended September 30
Balance December 31, 2024	$	(14,116)
Other comprehensive loss before reclassifications	(504)
Amounts reclassified from accumulated other comprehensive loss	1,161		(a)
Balance September 30, 2025	$	(13,459)
Balance December 31, 2023	$	(17,219)
Other comprehensive loss before reclassifications	(718)
Amounts reclassified from accumulated other comprehensive loss	1,351		(a)
Balance September 30, 2024	$	(16,586)

(a) These amounts primarily represent amortization of actuarial loss and are included in the computation of net periodic pension cost.  See Note 7.