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

9 Months Ended

Sep. 30, 2019

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 trust and other special use fund assets at September 30, 2019 and December 31, 2018 (dollars in thousands):  

	September 30, 2019
	Fair Value								Total Unrealized Gains		Total Unrealized Losses
Investment Type:	Nuclear Decommissioning Trust			Other Special Use Funds		Total
Equity securities	$	485,467		$	1,982	$	487,449		$	297,032	$	—
Available for sale-fixed income securities	483,528			240,582		724,110		(a)	28,750		(476		)
Other	(1,322		)	1,418		96		(b)	—		—
Total	$	967,673		$	243,982	$	1,211,655		$	325,782	$	(476	)

(a) As of September 30, 2019, the amortized cost basis of these available-for-sale investments is $696 million.

(b) Represents net pending securities sales and purchases.

	December 31, 2018
	Fair Value							Total Unrealized Gains		Total Unrealized Losses
Investment Type:	Nuclear Decommissioning Trust		Other Special Use Funds		Total
Equity securities	$	402,008	$	45,130	$	447,138		$	222,147	$	(459	)
Available for sale-fixed income securities	446,978		190,378		637,356		(a)	8,634		(6,778		)
Other	2,148		593		2,741		(b)	—		—
Total	$	851,134	$	236,101	$	1,087,235		$	230,781	$	(7,237	)

(a) As of December 31, 2018, the amortized cost basis of these available-for-sale investments is $635 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 for the three and nine months ended September 30, 2019 and 2018 (dollars in thousands):

	Three Months Ended September 30,
	Nuclear Decommissioning Trust			Other Special Use Funds		Total
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
2018
Realized gains	$	653		$	—	$	653
Realized losses	(1,965		)	—		(1,965		)
Proceeds from the sale of securities (a)	148,150			25,127		173,277

(a) Proceeds are reinvested in the nuclear decommissioning trust and coal reclamation escrow account.

	Nine Months Ended September 30,
	Nuclear Decommissioning Trust			Other Special Use Funds		Total
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
2018
Realized gains	$	2,951		$	1	$	2,952
Realized losses	(6,990		)	—		(6,990		)
Proceeds from the sale of securities (a)	401,396			41,644		443,040

(a)

Proceeds are reinvested in the nuclear decommissioning trust and coal reclamation escrow 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, 2019, is as follows (dollars in thousands):

	Nuclear Decommissioning Trust (a)		Coal Reclamation Escrow Account		Active Union Medical Trust		Total
Less than one year	$	40,309	$	32,628	$	37,013	$	109,950
1 year – 5 years	133,488		25,928		140,895		300,311
5 years – 10 years	103,973		720		—		104,693
Greater than 10 years	205,758		3,398		—		209,156
Total	$	483,528	$	62,674	$	177,908	$	724,110

(a)

Includes certain fixed income investments that are not due at a single maturity date. These investments have been allocated within the table based on the final payment date of the instrument.