Nuclear Decommissioning Trusts (Tables)

3 Months Ended

Mar. 31, 2017

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, 2017 and December 31, 2016 (dollars in thousands):

	Fair Value		Total Unrealized Gains		Total Unrealized Losses
March 31, 2017
Equity securities	$	374,695	$	207,708	$	—
Fixed income securities	430,016		10,022		(3,963		)
Net receivables (a)	337		—		—
Total	$	805,048	$	217,730	$	(3,963	)

	Fair Value		Total Unrealized Gains		Total Unrealized Losses
December 31, 2016
Equity securities	$	353,261	$	188,091	$	—
Fixed income securities	425,530		9,820		(4,962		)
Net receivables (a)	795		—		—
Total	$	779,586	$	197,911	$	(4,962	)

(a) Net receivables/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   March 31,
	2017			2016
Realized gains	$	2,367		$	2,438
Realized losses	(2,453		)	(1,786		)
Proceeds from the sale of securities (a)	151,126			141,809

(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, 2017 is as follows (dollars in thousands):

	Fair Value
Less than one year	$	12,143
1 year – 5 years	117,217
5 years – 10 years	114,131
Greater than 10 years	186,525
Total	$	430,016