Segment Information

9 Months Ended

Sep. 30, 2011

Segment Information [Abstract]

Segment Information

NOTE 13 - SEGMENT INFORMATION

Ameren has three reportable segments: Ameren Missouri, the Ameren Illinois Regulated Segment, and Merchant Generation. The Ameren Missouri segment for Ameren includes all the operations of Ameren Missouri's business as described in Note 1 - Summary of Significant Accounting Policies. The Ameren Illinois Regulated Segment for Ameren includes all of the regulated 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 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 and nine months ended September 30, 2011, and 2010, and total assets as of September 30, 2011, and December 31, 2010.

Three Months	Ameren Missouri		Ameren Illinois Regulated		Merchant Generation			Other			Intersegment Eliminations			Consolidated
2011:
External revenues	$	1,109	$	742	$	415		$	2		$	-		$	2,268
Intersegment revenues		6		3		67			2			(78	)		-
Net income (loss) attributable to Ameren Corporation(a)		190		98		(9	)		6			-			285
2010:
External revenues	$	1,053	$	743	$	470		$	1		$	-		$	2,267
Intersegment revenues		7		3		44			4			(58	)		-
Net income (loss) attributable to Ameren Corporation(a)		223		90		(470	)		(10	)		-			(167	)
Nine Months
2011:
External revenues	$	2,690	$	2,166	$	1,094		$	3		$	-		$	5,953
Intersegment revenues		19		10		163			3			(195	)		-
Net income (loss) attributable to Ameren Corporation(a)		301		168		26			(1	)		-			494
2010:
External revenues	$	2,486	$	2,296	$	1,149		$	1		$	-		$	5,932
Intersegment revenues		17		8		178			10			(213	)		-
Net income (loss) attributable to Ameren Corporation(a)		363		171		(428	)		(19	)		-			87
As of September 30, 2011:
Total assets	$	12,638	$	7,064	$	3,794		$	1,209		$	(1,349	)	$	23,356
As of December 31, 2010:
Total assets	$	12,504	$	7,406	$	3,934		$	1,354		$	(1,683	)	$	23,515

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