Selected Quarterly Information

12 Months Ended

Dec. 31, 2011

Selected Quarterly Information [Abstract]

SELECTED QUARTERLY INFORMATION (Unaudited) (In millions, except per share amounts)


Quarter Ended^(a)	Operating Revenues		Operating Income		Net Income (Loss) Attributable to Ameren Corporation			Earnings (Loss) per Common Share – Basic and Diluted
Ameren
March 31, 2011	$	1,904	$	227	$	71		$	0.29
March 31, 2010		1,940		298		102			0.43
June 30, 2011		1,781		316		138			0.57
June 30, 2010		1,725		331		152			0.64
September 30, 2011		2,268		550		285			1.18
September 30, 2010		2,267		89		(167	)		(0.70	)
December 31, 2011		1,578		148		25			0.10
December 31, 2010		1,706		198		52			0.21

(a)	The sum of quarterly amounts, including per share amounts, may not equal amounts reported for year-to-date periods. This is due to the effects of rounding and changes in the number of weighted-average shares outstanding each period.


Quarter Ended	Operating Revenues		Operating Income		Net Income (Loss)			Net Income (Loss) Available to Common Stockholder
Ameren Missouri
March 31, 2011	$	772	$	77	$	22		$	21
March 31, 2010		682		90		28			27
June 30, 2011		822		176		91			90
June 30, 2010		761		197		115			113
September 30, 2011		1,115		333		191			190
September 30, 2010		1,060		385		224			223
December 31, 2011		674		23		(14	)		(14	)
December 31, 2010		694		39		2			1


Quarter Ended	Operating Revenues		Operating Income		Income from Continuing Operations		Net Income		Net Income Available to Common Stockholder
Ameren Illinois
March 31, 2011	$	808	$	88	$	34	$	34	$	33
March 31, 2010		911		98		36		48		47
June 30, 2011		623		99		38		38		37
June 30, 2010		647		112		48		57		55
September 30, 2011		745		196		98		98		98
September 30, 2010		746		182		91		110		109
December 31, 2011		611		75		26		26		25
December 31, 2010		710		106		37		37		37


Quarter Ended	Operating Revenues		Operating Income (Loss)			Net Income (Loss)			Net Income (Loss) Attributable to Ameren Energy Generating Company
Genco
March 31, 2011	$	241	$	54		$	22		$	21
March 31, 2010		266		62			24			23
June 30, 2011		260		37			13			13
June 30, 2010		275		45			14			13
September 30, 2011		327		10			(4	)		(5	)
September 30, 2010		335		(99	)		(100	)		(101	)
December 31, 2011		238		38			14			15
December 31, 2010		250		54			26			26

- Definition

The entire disclosure for the quarterly financial data in the annual financial statements. The disclosure may include a tabular presentation of financial information for each fiscal quarter for the current and previous year, including revenues, gross profit, income or loss before extraordinary items and earnings per share data. It also includes an indication if the information in the note is unaudited, comments on the aggregate effect of year-end adjustments, and an explanation of matters or transactions that affect comparability or are pertinent to an understanding of the information furnished.

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