Nuclear Decommissioning Trusts (Tables)

6 Months Ended

Jun. 30, 2015

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, 2015 and December 31, 2014 (dollars in millions):

	Fair Value			Total Unrealized Gains		Total Unrealized Losses
June 30, 2015
Equity securities	$	314		$	160	$	—
Fixed income securities	414			13		(3		)
Net payables (a)	(4		)	—		—
Total	$	724		$	173	$	(3	)

	Fair Value			Total Unrealized Gains		Total Unrealized Losses
December 31, 2014
Equity securities	$	310		$	159	$	—
Fixed income securities	411			17		(1		)
Net payables (a)	(7		)	—		—
Total	$	714		$	176	$	(1	)

(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 millions):

	Three Months Ended   June 30,						Six Months Ended   June 30,
	2015			2014			2015			2014
Realized gains	$	1		$	1		$	2		$	2
Realized losses	(1		)	(1		)	(2		)	(3		)
Proceeds from the sale of securities (a)	110			96			226			199

(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, 2015 is as follows (dollars in millions):

	Fair Value
Less than one year	$	13
1 year – 5 years	111
5 years – 10 years	123
Greater than 10 years	167
Total	$	414