Nuclear Decommissioning Trusts (Tables)

6 Months Ended

Jun. 30, 2016

Investments, Debt and Equity Securities [Abstract]

Fair value of APS's nuclear decommissioning trust fund assets

The following table includes the unrealized gains and losses based on the original cost of the investment and summarizes the fair value of APS’s nuclear decommissioning trust fund assets at June 30, 2016 and December 31, 2015 (dollars in thousands):

	Fair Value			Total Unrealized Gains		Total Unrealized Losses
June 30, 2016
Equity securities	$	328,037		$	165,926	$	(7	)
Fixed income securities	452,518			22,953		(345		)
Net payables (a)	(13,139		)	—		—
Total	$	767,416		$	188,879	$	(352	)

	Fair Value			Total Unrealized Gains		Total Unrealized Losses
December 31, 2015
Equity securities	$	314,957		$	157,098	$	(115	)
Fixed income securities	420,574			11,955		(2,645		)
Net payables (a)	(335		)	—		—
Total	$	735,196		$	169,053	$	(2,760	)

(a) Net payables relate to pending purchases and sales of securities.

Realized gains and losses and proceeds from the sale of securities by the nuclear decommissioning trust funds

The following table sets forth approximate gains and losses and proceeds from the sale of securities by the nuclear decommissioning trust funds (dollars in thousands):

	Three Months Ended   June 30,						Six Months Ended   June 30,
	2016			2015			2016			2015
Realized gains	$	2,282		$	1,260		$	4,720		$	2,455
Realized losses	(1,350		)	(1,525		)	(3,136		)	(2,050		)
Proceeds from the sale of securities (a)	148,785			110,498			290,594			225,779

(a) Proceeds are reinvested in the trust.

Fair value of fixed income securities, summarized by contractual maturities

The fair value of fixed income securities, summarized by contractual maturities, at June 30, 2016 is as follows (dollars in thousands):

	Fair Value
Less than one year	$	13,046
1 year – 5 years	133,548
5 years – 10 years	103,874
Greater than 10 years	202,050
Total	$	452,518