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

6 Months Ended

Jun. 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):  

	June 30, 2020
	Fair Value									Total Unrealized Gains		Total Unrealized Losses
Investment Type:	Nuclear Decommissioning Trusts			Other Special Use Funds		Total
Equity securities	$	518,236		$	8,955	$	527,191			$	316,494	$	(58	)
Available for sale-fixed income securities	511,927			243,851		755,778			(a)	49,693		(524		)
Other	(6,130		)	526		(5,604		)	(b)	—		—
Total	$	1,024,033		$	253,332	$	1,277,365			$	366,187	$	(582	)

(a) As of June 30, 2020, the amortized cost basis of these available-for-sale investments is $707 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 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 June 30,
	Nuclear Decommissioning Trusts			Other Special Use Funds		Total
2020
Realized gains	$	4,500		$	—	$	4,500
Realized losses	(1,621		)	—		(1,621		)
Proceeds from the sale of securities (a)	176,942			19,830		196,772
2019
Realized gains	$	2,643		$	—	$	2,643
Realized losses	(1,700		)	—		(1,700		)
Proceeds from the sale of securities (a)	93,559			36,747		130,306

(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.

	Six Months Ended June 30,
	Nuclear Decommissioning Trusts			Other Special Use Funds		Total
2020
Realized gains	$	7,813		$	—	$	7,813
Realized losses	(3,848		)	—		(3,848		)
Proceeds from the sale of securities (a)	355,138			36,721		391,859
2019
Realized gains	$	3,746		$	—	$	3,746
Realized losses	(3,105		)	—		(3,105		)
Proceeds from the sale of securities (a)	216,152			93,202		309,354

(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 June 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	$	21,767	$	37,494	$	40,673	$	99,934
1 year – 5 years	137,754		11,371		143,406		292,531
5 years – 10 years	125,807		1,904		—		127,711
Greater than 10 years	226,599		9,003		—		235,602
Total	$	511,927	$	59,772	$	184,079	$	755,778