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

9 Months Ended

Sep. 30, 2020

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):  

	September 30, 2020
	Fair Value							Total Unrealized Gains		Total Unrealized Losses
Investment Type:	Nuclear Decommissioning Trusts		Other Special Use Funds		Total
Equity securities	$	570,382	$	8,090	$	578,472		$	359,112	$	(36)
Available for sale-fixed income securities	513,603		258,758		772,361		(a)	47,158		(674)
Other	(14,148)		1,444		(12,704)		(b)	—		—
Total	$	1,069,837	$	268,292	$	1,338,129		$	406,270	$	(710)

(a)As of September 30, 2020, the amortized cost basis of these available-for-sale investments is $726 million.

(b)Represents net pending securities sales and purchases.

	December 31, 2019
	Fair Value							Total Unrealized Gains		Total Unrealized Losses
Investment Type:	Nuclear Decommissioning Trusts		Other Special Use Funds		Total
Equity securities	$	529,716	$	7,142	$	536,858		$	337,681	$	—
Available for sale-fixed income securities	478,658		237,479		716,137		(a)	25,795		(669)
Other	2,401		474		2,875		(b)	—		—
Total	$	1,010,775	$	245,095	$	1,255,870		$	363,476	$	(669)

(a)As of December 31, 2019, the amortized cost basis of these available-for-sale investments is $691 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 tables set 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 September 30,
	Nuclear Decommissioning Trusts		Other Special Use Funds		Total
2020
Realized gains	$	2,933	$	—	$	2,933
Realized losses	(750)		(15)		(765)
Proceeds from the sale of securities (a)	178,919		37,107		216,026
2019
Realized gains	$	4,732	$	4	$	4,736
Realized losses	(2,360)		—		(2,360)
Proceeds from the sale of securities (a)	155,386		56,255		211,641

(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.

	Nine Months Ended September 30,
	Nuclear Decommissioning Trusts		Other Special Use Funds		Total
2020
Realized gains	$	10,746	$	—	$	10,746
Realized losses	(4,598)		(15)		(4,613)
Proceeds from the sale of securities (a)	534,057		73,828		607,885
2019
Realized gains	$	8,478	$	4	$	8,482
Realized losses	(5,465)		—		(5,465)
Proceeds from the sale of securities (a)	371,538		149,458		520,996

(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 September 30, 2020, is as follows (dollars in thousands):

	Nuclear Decommissioning Trust		Coal Mine Reclamation Escrow Account		Active Union Employee Medical Account		Total
Less than one year	$	23,079	$	34,578	$	40,506	$	98,163
1 year – 5 years	146,885		29,041		142,938		318,864
5 years – 10 years	122,619		2,772		—		125,391
Greater than 10 years	221,020		8,923		—		229,943
Total	$	513,603	$	75,314	$	183,444	$	772,361