Segment Information

12 Months Ended

Dec. 31, 2012

Segment Reporting Information, Profit (Loss) [Abstract]

SEGMENT INFORMATION

SEGMENT INFORMATION

Ameren has three reportable segments: Ameren Missouri, Ameren Illinois, and Merchant Generation. The Ameren Missouri segment includes all the operations of Ameren Missouri’s business as described in Note 1 - Summary of Significant Accounting Policies. The Ameren Illinois segment 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 consisted primarily of the operations or activities of AER, including Genco, EEI, AERG, and Marketing Company. Ameren is divesting its Merchant Generation segment and therefore has excluded that segment's information below. See Note 16 - Divestiture Transactions and Discontinued Operations for information regarding the Merchant Generation segment. The category called Other primarily includes Ameren parent company activities, Ameren Services, and ATXI. The Other category also includes activities previously included in the Merchant Generation segment that will be retained by Ameren after the divestiture of New AER and the sale of the Elgin, Gibson City, and Grand Tower gas-fired energy centers are complete. See Note 16 - Divestiture Transactions and Discontinued Operations for information regarding the assets and liabilities to be retained by Ameren after the divestitures.

The following table presents information about the reported revenues and specified items reflected in net income attributable to Ameren Corporation from continuing operations 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		Other				Intersegment Eliminations			Consolidated
2012
External revenues	$	3,252	$	2,524	$	5			$	—		$	5,781
Intersegment revenues	20		1		3				(24		)	—
Depreciation and amortization	440		221		6				—			667
Interest and dividend income	32		—		—				—			32
Interest charges	223		129		39				—			391
Income taxes (benefit)	252		94		(37		)		—			309
Net income (loss) attributable to Ameren Corporation from continuing operations	416		141		(39		)		—			518
Capital expenditures	595		442		26				—			1,063
Total assets	13,043		7,282		1,228				(934		)	20,619		(a)
2011
External revenues	$	3,360	$	2,784	$	83			$	—		$	6,227
Intersegment revenues	23		3		3				(29		)	—
Depreciation and amortization	408		215		23				—			646
Interest and dividend income	30		1		—				—			31
Interest charges	209		136		42				—			387
Income taxes (benefit)	161		127		(43		)		—			245
Net income (loss) attributable to Ameren Corporation from continuing operations	287		193		(62		)		—			418
Capital expenditures	550		351		(20		)	(b)	—			881
Total assets	12,757		7,213		1,211				(1,176		)	20,005		(a)
2010
External revenues	$	3,180	$	3,012	$	77			$	—		$	6,269
Intersegment revenues	17		2		—				(19		)	—
Depreciation and amortization	382		210		35				—			627
Interest and dividend income	31		1		—				—			32
Interest charges	213		143		59				—			415
Income taxes (benefit)	199		137		(62		)		—			274
Net income (loss) attributable to Ameren Corporation from continuing operations	364		208		(89		)		—			483
Capital expenditures	624		281		36				—			941
Total assets	12,504		7,406		1,354				(1,541		)	19,723		(a)

(a) Excludes "Current assets for discontinued operations." See Note 16 - Divestiture Transactions and Discontinued Operations for additional information.

(b) Includes the elimination of intercompany transfers.