Nuclear Decommissioning Trust Fund Investments (Tables)

12 Months Ended

Dec. 31, 2013

Nuclear Decommissioning Trust Fund Investments [Line Items]

Fair Value Of Securities In Nuclear Decommissioning Trust Fund

The following table presents the costs and fair values of investments in debt and equity securities in Ameren Missouri’s nuclear decommissioning trust fund at December 31, 2013, and 2012:

Security Type	Cost		Gross Unrealized Gain			Gross Unrealized Loss	Fair Value
2013
Debt securities	$	157	$	4	$	2	$	159
Equity securities	137		199			4	332
Cash	3		—			—	3
Other(b)	(a)		—			—	(a)
Total	$	297	$	203	$	6	$	494
2012
Debt securities	$	133	$	8	$	(a)	$	141
Equity securities	145		130			11	264
Cash	1		—			—	1
Other(b)	2		—			—	2
Total	$	281	$	138	$	11	$	408

(a) Amount less than $1 million.

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

Schedule Of Unrealized Losses On Available-For-Sale Investments Included In Nuclear Decommissioning Trust Fund

They are aggregated by investment category and the length of time that individual securities have been in a continuous unrealized loss position at December 31, 2013:

	Less than 12 Months					12 Months or Greater			Total
	Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses	Fair Value		Gross Unrealized Losses
Debt securities	$	72	$	2	$	(a)	$	(a)	$	72	$	2
Equity securities	6		(a)			7		4	13		4
Total	$	78	$	2	$	7	$	4	$	85	$	6

(a) Amount less than $1 million.

Regulatory Asset

Nuclear Decommissioning Trust Fund Investments [Line Items]

Proceeds From Sale Of Investments In Nuclear Decommissioning Trust Fund And Gross Realized Gains And Losses

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, 2013, 2012, and 2011:

	2013		2012		2011
Proceeds from sales and maturities	$	196	$	384	$	199
Gross realized gains	7		6		5
Gross realized losses	5		2		4

Fair Value Of Securities In Nuclear Decommissioning Trust Fund According To Their Contractual Maturities

The following table presents the costs and fair values of investments in debt securities in Ameren Missouri’s nuclear decommissioning trust fund according to their contractual maturities at December 31, 2013:

	Cost		Fair Value
Less than 5 years	$	93	$	94
5 years to 10 years	31		32
Due after 10 years	33		33
Total	$	157	$	159