Nuclear Decommissioning Trusts (Tables)

3 Months Ended

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

	Fair Value			Total Unrealized Gains		Total Unrealized Losses
March 31, 2015
Equity securities	$	313		$	161	$	—
Fixed income securities	416			20		(1		)
Net payables (a)	(2		)	—		—
Total	$	727		$	181	$	(1	)

	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   March 31,
	2015			2014
Realized gains	$	1		$	1
Realized losses	(1		)	(2		)
Proceeds from the sale of securities (a)	115			103

(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 March 31, 2015 is as follows (dollars in millions):

	Fair Value
Less than one year	$	16
1 year – 5 years	113
5 years – 10 years	118
Greater than 10 years	169
Total	$	416