Segment Information

3 Months Ended

Mar. 31, 2012

Segment Information [Abstract]

Segment Information

NOTE 13 - SEGMENT INFORMATION

Ameren has three reportable segments: Ameren Missouri, Ameren Illinois, and Merchant Generation. The Ameren Missouri segment for Ameren and Ameren Missouri includes all the operations of Ameren Missouri's business as described in Note 1 - Summary of Significant Accounting Policies. The Ameren Illinois segment for Ameren and Ameren Illinois includes all of the operations of Ameren Illinois' business as described in Note 1 - Summary of Significant Accounting Policies. The Merchant Generation segment for Ameren consists primarily of the operations or activities of Genco, including EEI, AERG, Medina Valley through February 2012, and Marketing Company. The category called Other primarily includes Ameren parent company activities, Ameren Services, and ATXI.

The following table presents information about the reported revenues and specified items included in Ameren's net income for the three months ended March 31, 2012, and 2011, and total assets as of March 31, 2012, and December 31, 2011.

Three Months	Ameren Missouri		Ameren Illinois		Merchant Generation			Other			Intersegment Eliminations			Consolidated
2012:
External revenues	$	686	$	721	$	249		$	1		$	1		$	1,658
Intersegment revenues		5		3		87			1			(96	)		-
Net income (loss) attributable to Ameren Corporation(a)		21		27		(363	)		(88	)		-			(403	)
2011:
External revenues	$	767	$	805	$	332		$	-		$	-		$	1,904
Intersegment revenues		5		3		47			1			(56	)		-
Net income (loss) attributable to Ameren Corporation(a)		21		33		20			(3	)		-			71
As of March 31, 2012:
Total assets	$	12,546	$	7,256	$	3,266		$	1,261		$	(1,430	)	$	22,899
As of December 31, 2011:
Total assets	$	12,757	$	7,213	$	3,833		$	1,211		$	(1,369	)	$	23,645

(a) Represents net income (loss) available to common stockholders.