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

3 Months Ended

Mar. 31, 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 at March 31, 2020 and December 31, 2019 (dollars in thousands):  

	March 31, 2020
	Fair Value							Total Unrealized Gains		Total Unrealized Losses
Investment Type:	Nuclear Decommissioning Trusts		Other Special Use Funds		Total
Equity securities	$	427,915	$	6,752	$	434,667		$	234,695	$	(1,201	)
Available for sale-fixed income securities	490,421		244,640		735,061		(a)	41,455		(3,527		)
Other	2,090		1,331		3,421		(b)	—		—
Total	$	920,426	$	252,723	$	1,173,149		$	276,150	$	(4,728	)

(a) As of March 31, 2020, the amortized cost basis of these available-for-sale investments is $697 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 for the three months ended March 31, 2020 and 2019 (dollars in thousands):

	Three Months Ended March 31,
	Nuclear Decommissioning Trusts			Other Special Use Funds		Total
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
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

(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, 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	$	11,911	$	37,498	$	40,872	$	90,281
1 year – 5 years	137,509		18,487		143,565		299,561
5 years – 10 years	112,834		—		—		112,834
Greater than 10 years	228,167		4,218		—		232,385
Total	$	490,421	$	60,203	$	184,437	$	735,061