Nuclear Decommissioning Trust Fund Investments (Tables)

12 Months Ended

Dec. 31, 2016

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'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.

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, 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

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'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