Nuclear Decommissioning Trust Fund Investments

12 Months Ended

Dec. 31, 2016

Investments, Debt and Equity Securities [Abstract]

NUCLEAR DECOMMISSIONING TRUST FUND INVESTMENTS

NUCLEAR DECOMMISSIONING TRUST FUND INVESTMENTS

Ameren Missouri has investments in debt and equity securities that are held in a trust fund for the purpose of funding the decommissioning of its Callaway energy center. We have classified these investments as available for sale, and we have recorded all such investments at their fair market value at December 31, 2016, and 2015. See Note 10 – Callaway Energy Center for additional information.

Investments in the nuclear decommissioning trust fund have a target allocation of 60% to 70% in equity securities, with the balance invested in debt securities.

The following table presents proceeds from the sale and maturities of investments in Ameren Missouri’s nuclear decommissioning trust fund and the gross realized gains and losses resulting from those sales for the years ended December 31, 2016, 2015, and 2014:

	2016		2015		2014
Proceeds from sales and maturities	$	377	$	349	$	391
Gross realized gains	7		8		7
Gross realized losses	4		2		2

Net realized and unrealized gains and losses are deferred and are currently recorded as a regulatory liability related to AROs on Ameren’s and Ameren Missouri’s balance sheets. This reporting is consistent with the method used to account for the decommissioning costs recovered in rates. Gains or losses associated with assets in the trust fund could result in lower or higher funding requirements for decommissioning costs, which are expected to be reflected in electric rates paid by Ameren Missouri’s customers. See Note 2 – Rate and Regulatory Matters.

The following table presents the costs and fair values of investments in debt and equity securities in Ameren's and Ameren Missouri’s nuclear decommissioning trust fund at December 31, 2016 and 2015:

Security Type	Cost			Gross Unrealized Gain			Gross Unrealized Loss	Fair Value
2016
Debt securities	$	197		$	3	$	4	$	196
Equity securities	161			253			6	408
Cash	1			—			—	1
Other(a)	2			—			—	2
Total	$	361		$	256	$	10	$	607
2015
Debt securities	$	191		$	2	$	4	$	189
Equity securities	147			224			7	364
Cash	4			—			—	4
Other(a)	(1		)	—			—	(1		)
Total	$	341		$	226	$	11	$	556

(a) Represents net receivables and payables relating to pending security sales, interest, and security purchases.

The following table presents the costs and fair values of investments in debt securities in Ameren's and Ameren Missouri’s nuclear decommissioning trust fund according to their contractual maturities at December 31, 2016:

	Cost		Fair Value
Less than 5 years	$	105	$	104
5 years to 10 years	47		47
Due after 10 years	45		45
Total	$	197	$	196

We have unrealized losses relating to certain available-for-sale investments included in our nuclear decommissioning trust fund, recorded as a regulatory asset as discussed above. Decommissioning will not occur until our nuclear energy center is retired. The Callaway energy center’s current operating license expires in 2044.