Schedule II - Valuation And Qualifying Accounts

12 Months Ended

Dec. 31, 2012

Valuation and Qualifying Accounts [Abstract]

Valuation And Qualifying Accounts

SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS FOR THE YEARS ENDED DECEMBER 31, 2012, 2011 AND 2010
(in millions)
Column A	Column B		Column C				Column D		Column E
Description	Balance at Beginning of Period		(1) Charged to Costs and Expenses		(2) Charged to Other Accounts(a)		Deductions(b)		Balance at End of Period
Ameren:
Deducted from assets - allowance for doubtful accounts:
2012	$	20	$	30	$	2	$	35	$	17
2011	23		41		—		44		20
2010	24		33		—		34		23
Deferred tax valuation allowance:
2012	$	2	$	2	$	—	$	—	$	4
2011	2		—		—		—		2
2010	—		2		—		—		2
Ameren Missouri:
Deducted from assets - allowance for doubtful accounts:
2012	$	7	$	11	$	—	$	13	$	5
2011	8		17		—		18		7
2010	6		14		—		12		8
Deferred tax valuation allowance:
2012	$	1	$	—	$	—	$	—	$	1
2011	1		—		—		—		1
2010	—		1		—		—		1
Ameren Illinois:
Deducted from assets - allowance for doubtful accounts:
2012	$	13	$	19	$	2	$	22	$	12
2011	13		24		—		24		13
2010	17		18		—		22		13
Deferred tax valuation allowance:
2012	$	—	$	1	$	—	$	—	$	1
2011	—		—		—		—		—
2010	—		—		—		—		—

(a) Uncollectible account reserve associated with receivables purchased by Ameren Illinois from alternative retail electric suppliers as required by the Illinois Public Utility Act.

(b) Uncollectible accounts charged off, less recoveries.