Nuclear Decommissioning Trusts (Tables)

12 Months Ended

Dec. 31, 2014

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 December 31, 2014 and December 31, 2013 (dollars in millions):

	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	)

	Fair Value			Total  Unrealized  Gains		Total  Unrealized  Losses
December 31, 2013
Equity securities	$	272		$	129	$	—
Fixed income securities	373			11		(6		)
Net payables (a)	(3		)	—		—
Total	$	642		$	140	$	(6	)

(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):

	Year Ended December 31,
	2014			2013			2012
Realized gains	$	5		$	6		$	7
Realized losses	(5		)	(7		)	(4		)
Proceeds from the sale of securities (a)	356			446			418

(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 December 31, 2014 is as follows (dollars in millions):

	Fair Value
Less than one year	$	14
1 year – 5 years	116
5 years – 10 years	122
Greater than 10 years	159
Total	$	411