Summary Of Significant Accounting Policies (Tables)

6 Months Ended

Jun. 30, 2012

Schedule Of Excise Taxes

	Three Months				Six Months
	2012		2011		2012		2011
Ameren Missouri	$	38	$	34	$	65	$	63
Ameren Illinois		10		10		28		32
Ameren	$	48	$	44	$	93	$	95

Schedule Of Equity Changes To The Noncontrolling Interest

	Three Months						Six Months
	2012			2011			2012			2011
Ameren:
Noncontrolling interests, beginning of period	$	147		$	155		$	149		$	154
Net income (loss) attributable to noncontrolling interests		(1	)		1			(1	)		4
Dividends paid to noncontrolling interest holders		(1	)		(1	)		(3	)		(3	)
Noncontrolling interests, end of period	$	145		$	155		$	145		$	155
Genco:
Noncontrolling interest, beginning of period	$	5		$	12		$	7		$	11
Net income (loss) attributable to noncontrolling interest		(2	)		-			(4	)		1
Noncontrolling interest, end of period	$	3		$	12		$	3		$	12

Ameren Illinois Company [Member]

Schedule Of Excise Taxes

	Three Months				Six Months
	2012		2011		2012		2011
Ameren Missouri	$	38	$	34	$	65	$	63
Ameren Illinois		10		10		28		32
Ameren	$	48	$	44	$	93	$	95

Ameren Energy Generating Company [Member]

Schedule Of Equity Changes To The Noncontrolling Interest

	Three Months						Six Months
	2012			2011			2012			2011
Ameren:
Noncontrolling interests, beginning of period	$	147		$	155		$	149		$	154
Net income (loss) attributable to noncontrolling interests		(1	)		1			(1	)		4
Dividends paid to noncontrolling interest holders		(1	)		(1	)		(3	)		(3	)
Noncontrolling interests, end of period	$	145		$	155		$	145		$	155
Genco:
Noncontrolling interest, beginning of period	$	5		$	12		$	7		$	11
Net income (loss) attributable to noncontrolling interest		(2	)		-			(4	)		1
Noncontrolling interest, end of period	$	3		$	12		$	3		$	12

Union Electric Company [Member]

Schedule Of Excise Taxes

	Three Months				Six Months
	2012		2011		2012		2011
Ameren Missouri	$	38	$	34	$	65	$	63
Ameren Illinois		10		10		28		32
Ameren	$	48	$	44	$	93	$	95