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

3 Months Ended

Mar. 31, 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 March 31, 2019 and December 31, 2018 (dollars in thousands):  

	March 31, 2019
	Fair Value							Total Unrealized Gains		Total Unrealized Losses
Investment Type:	Nuclear Decommissioning Trusts		Other Special Use Funds		Total
Equity securities	$	458,776	$	11,471	$	470,247		$	273,817	$	(4	)
Available for sale-fixed income securities	457,903		225,173		683,076		(a)	15,306		(2,250		)
Other	2,630		1,563		4,193		(b)	—		—
Total	$	919,309	$	238,207	$	1,157,516		$	289,123	$	(2,254	)

(a) As of March 31, 2019, the amortized cost basis of these available-for-sale investments is $670 million.

(b) Represents net pending securities sales and purchases.

	December 31, 2018
	Fair Value							Total Unrealized Gains		Total Unrealized Losses
Investment Type:	Nuclear Decommissioning Trusts		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 months ended March 31, 2019 and 2018 (dollars in thousands):

	Three Months Ended March 31,
	Nuclear Decommissioning Trusts			Other Special Use Funds		Total
2019
Realized gains	$	1,103		$	—	$	1,103
Realized losses	(1,405		)	—		(1,405		)
Proceeds from the sale of securities (a)	122,593			56,455		179,048
2018
Realized gains	$	814		$	1	$	815
Realized losses	(2,047		)	—		(2,047		)
Proceeds from the sale of securities (a)	130,456			2,555		133,011

(a) Proceeds are reinvested in the nuclear decommissioning trusts or other special use funds.

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, 2019, is as follows (dollars in thousands):

	Nuclear Decommissioning Trusts (a)		Coal Reclamation Escrow Accounts		Active Union Medical Trust		Total
Less than one year	$	26,100	$	20,085	$	40,099	$	86,284
1 year – 5 years	120,511		15,960		138,627		275,098
5 years – 10 years	120,342		3,581		—		123,923
Greater than 10 years	190,950		6,821		—		197,771
Total	$	457,903	$	46,447	$	178,726	$	683,076

(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.