Investments in Nuclear Decommissioning Trusts and Other Special Use Funds (Tables)

3 Months Ended

Mar. 31, 2021

Investments, Debt and Equity Securities [Abstract]

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 summarizes the fair value of APS’s nuclear decommissioning trusts and other special use fund assets (dollars in thousands):  

	March 31, 2021
	Fair Value							Total Unrealized Gains		Total Unrealized Losses
Investment Type:	Nuclear Decommissioning Trusts		Other Special Use Funds		Total
Equity securities	$	670,359	$	19,211	$	689,570		$	457,442	$	—
Available for sale-fixed income securities	504,878		336,894		841,772		(a)	27,338		(3,203)
Other	(15,538)		1,401		(14,137)		(b)	—		—
Total	$	1,159,699	$	357,506	$	1,517,205		$	484,780	$	(3,203)

(a)As of March 31, 2021, the amortized cost basis of these available-for-sale investments is $818 million.

(b)Represents net pending securities sales and purchases.

	December 31, 2020
	Fair Value							Total Unrealized Gains		Total Unrealized Losses
Investment Type:	Nuclear Decommissioning Trusts		Other Special Use Funds		Total
Equity securities	$	639,851	$	37,337	$	677,188		$	421,666	$	—
Available for sale-fixed income securities	516,412		216,668		733,080		(a)	46,581		(398)
Other	(17,828)		504		(17,324)		(b)	—		—
Total	$	1,138,435	$	254,509	$	1,392,944		$	468,247	$	(398)

(a)As of December 31, 2020, the amortized cost basis of these available-for-sale investments is $687 million.

(b)Represents net pending securities sales and purchases.

Realized gains and losses and proceeds from the sale of securities by the nuclear decommissioning trust funds

The following table sets forth APS’s 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 Trusts		Other Special Use Funds		Total
2021
Realized gains	$	2,968	$	—	$	2,968
Realized losses	(4,148)		—		(4,148)
Proceeds from the sale of securities (a)	234,728		145,250		379,978
2020
Realized gains	$	3,313	$	—	$	3,313
Realized losses	(2,227)		—		(2,227)
Proceeds from the sale of securities (a)	178,196		16,891		195,087

(a)    Proceeds are reinvested in the nuclear decommissioning trusts and other special use funds, excluding amounts reimbursed to the Company for active union employee medical claims from the active union employee medical account.

Fair value of fixed income securities, summarized by contractual maturities

The fair value of APS’s fixed income securities, summarized by contractual maturities, at March 31, 2021, is as follows (dollars in thousands):

	Nuclear Decommissioning Trust		Coal Reclamation Escrow Account		Active Union Employee Medical Account		Total
Less than one year	$	25,048	$	26,259	$	40,469	$	91,776
1 year – 5 years	147,347		34,936		160,324		342,607
5 years – 10 years	137,479		2,708		63,477		203,664
Greater than 10 years	195,004		8,721		—		203,725
Total	$	504,878	$	72,624	$	264,270	$	841,772