v3.25.1
Investments in Nuclear Decommissioning Trusts and Other Special Use Funds (Tables)
 3 Months Ended
Mar. 31, 2025
Investments, Debt and Equity Securities [Abstract]  
Schedule of Fair Value of APS's Nuclear Decommissioning Trust Fund Assets
The following tables present the unrealized gains and losses based on the original cost of the investment and summarize the fair value of the nuclear decommissioning trusts and other special use fund assets (dollars in thousands): 
March 31, 2025
 Fair ValueTotal
Unrealized
Gains		Total
Unrealized
Losses
Investment Type:Nuclear Decommissioning TrustsOther Special Use FundsTotal
Equity securities$416,753 $37,234 $453,987 $341,566 $(325)
Available for sale-fixed income securities866,658 376,137 1,242,795 (a)13,416 (22,318)
Other2,690 2,030 4,720 (b)— — 
Total$1,286,101 $415,401 $1,701,502 (c)$354,982 $(22,643)
(a)As of March 31, 2025, the amortized cost basis of these available-for-sale investments is $1,252 million.
(b)Represents net pending securities sales and purchases.
(c)All amounts pertain to APS, with the exception of $35.1 million of other special use fund investments in equity securities relating to the Captive.
December 31, 2024
 Fair ValueTotal
Unrealized
Gains		Total
Unrealized
Losses
Investment Type:Nuclear Decommissioning TrustsOther Special Use FundsTotal
Equity securities$435,470 $24,962 $460,432 $359,127 $(176)
Available for sale-fixed income securities844,040 355,544 1,199,584 (a)7,717 (31,960)
Other3,335 27,851 31,186 (b)— — 
Total$1,282,845 $408,357 $1,691,202 (c)$366,844 $(32,136)
(a)As of December 31, 2024, the amortized cost basis of these available-for-sale investments is $1,224 million.
(b)Represents net pending securities sales and purchases.
(c)All amounts pertain to APS, with the exception of $34.2 million of other special use fund investments in equity securities relating to the Captive.
Schedule of Realized Gains and Losses and Proceeds from the Sale of Securities by the Nuclear Decommissioning Trust Funds
The following table sets forth realized gains and losses relating to the sale and maturity of available-for-sale debt securities and equity securities, and the proceeds from the sale and maturity of these investment securities (dollars in thousands):
 Three Months Ended March 31,
 Nuclear Decommissioning TrustsOther Special Use FundsTotal
2025
Realized gains$1,658 $— $1,658 
Realized losses$(2,761)$— $(2,761)
Proceeds from the sale of securities (a)$416,601 $69,213 (b)$485,814 
2024
Realized gains$54,492 $80 $54,572 
Realized losses$(2,815)$— $(2,815)
Proceeds from the sale of securities (a)$377,822 $66,048 $443,870 

(a)    Proceeds are reinvested in the nuclear decommissioning trusts and other special use funds, excluding investment fees and amounts reimbursed to the Company for active union employee medical claims from the active union employee medical account.
(b) All amounts pertain to APS, with the exception of $25.3 million of other special use fund proceeds from the sale of securities relating to the Captive.
Schedule of Fair Value of Fixed Income Securities, Summarized by Contractual Maturities
The fair value fixed income securities summarized by contractual maturities as of March 31, 2025 is as follows (dollars in thousands):
 
 Nuclear Decommissioning TrustsCoal Reclamation Escrow AccountActive Union Employee Medical Account
Captive Insurance Cell (a)
Total
Less than one year$32,422 $90,167 $39,464 25,149 $187,202 
1 year – 5 years292,409 48,289 157,055 — 497,753 
5 years – 10 years137,989 — 16,013 — 154,002 
Greater than 10 years403,838 — — — 403,838 
Total$866,658 $138,456 $212,532 25,149 $1,242,795 
(a)All amounts pertain to APS, with the exception of $25.1 million of other special use fund investments in fixed income securities relating to the Captive.