Segment Information (Tables)

12 Months Ended

Dec. 31, 2012

Segment Reporting Information, Profit (Loss) [Abstract]

Schedule Of Segment Reporting Information, By Segment

The following table presents information about the reported revenues and specified items reflected in Ameren’s net income for the years ended December 31, 2012, 2011, and 2010, and total assets as of December 31, 2012, 2011, and 2010.

Ameren

	Ameren Missouri		Ameren Illinois Segment		Merchant Generation				Other				Intersegment Eliminations			Consolidated
2012
External revenues	$	3,251	$	2,509	$	1,063			$	5			$	—		$	6,828
Intersegment revenues	21		16		310				4				(351		)	—
Depreciation and amortization	440		221		102				12				—			775
Interest and dividend income	32		—		—				40				(39		)	33
Interest charges	223		129		95				38				(37		)	448
Income taxes (benefit)	252		94		(1,019		)		(7		)		—			(680		)
Net income (loss) attributable to Ameren Corporation(a)	416		141		(1,516		)	(b)	(15		)		—			(974		)
Capital expenditures	595		442		178				25				—			1,240
Total assets	13,043		7,282		1,300				1,228				(1,018		)	21,835
2011
External revenues	$	3,358	$	2,774	$	1,394			$	5			$	—		$	7,531
Intersegment revenues	25		13		235				4				(277		)	—
Depreciation and amortization	408		215		143				19				—			785
Interest and dividend income	30		1		—				44				(43		)	32
Interest charges	209		136		105				44				(43		)	451
Income taxes (benefit)	161		127		32				(10		)		—			310
Net income (loss) attributable to Ameren Corporation(a)	287		193		45				(6		)		—			519
Capital expenditures	550		351		153				(24		)	(c)	—			1,030
Total assets	12,757		7,213		3,833				1,211				(1,369		)	23,645
2010
External revenues	$	3,176	$	3,002	$	1,459			$	1			$	—		$	7,638
Intersegment revenues	21		12		234				13				(280		)	—
Depreciation and amortization	382		210		146				27				—			765
Interest and dividend income	31		1		1				25				(25		)	33
Interest charges	213		143		133				35				(27		)	497
Income taxes (benefit)	199		137		6				(17		)		—			325
Net income (loss) attributable to Ameren Corporation(a)	364		208		(409		)	(b)	(24		)		—			139
Capital expenditures	624		281		101				36				—			1,042
Total assets	12,504		7,406		3,934				1,354				(1,687		)	23,511

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

(b) Includes noncash impairment and other charges, which were $2,578 million and $589 million before tax, recognized during the years ended December 31, 2012, and 2010, respectively. See Note 17 - Impairment and Other Charges for additional information.

(c) Includes the elimination of intercompany transfers.