Retirement Benefits (Tables)

6 Months Ended

Jun. 30, 2012

	Pension Benefits^(a)												Postretirement Benefits^(a)
	Three Months						Six Months						Three Months						Six Months
	2012			2011			2012			2011			2012			2011			2012			2011
Service cost	$	20		$	18		$	41		$	38		$	6		$	5		$	12		$	11
Interest cost		42			45			85			90			12			14			26			29
Expected return on plan assets		(53	)		(54	)		(107	)		(108	)		(15	)		(13	)		(29	)		(27	)
Amortization of:
Transition obligation		-			-			-			-			1			1			1			1
Prior service cost (benefit)		(1	)		(1	)		(1	)		(1	)		(2	)		(2	)		(3	)		(4	)
Actuarial loss		19			10			39			21			-			1			4			2
Net periodic benefit cost	$	27		$	18		$	57		$	40		$	2		$	6		$	11		$	12

(a)	Includes amounts for Ameren registrant and nonregistrant subsidiaries.

Summary Of Benefit Plan Costs Incurred

	Pension Costs								Postretirement Costs
	Three Months				Six Months				Three Months				Six Months
	2012		2011		2012		2011		2012		2011		2012		2011
Ameren Missouri	$	16	$	12	$	32	$	26	$	-	$	2	$	5	$	5
Ameren Illinois		8		3		18		8		-		4		2		6
Genco		2		3		5		5		2		-		4		1
Other		1		-		2		1		-		-		-		-
Ameren^(a)	$	27	$	18	$	57	$	40	$	2	$	6	$	11	$	12

(a)	Includes amounts for Ameren registrant and nonregistrant subsidiaries.

Ameren Missouri [Member]

Summary Of Benefit Plan Costs Incurred

	Pension Costs								Postretirement Costs
	Three Months				Six Months				Three Months				Six Months
	2012		2011		2012		2011		2012		2011		2012		2011
Ameren Missouri	$	16	$	12	$	32	$	26	$	-	$	2	$	5	$	5
Ameren Illinois		8		3		18		8		-		4		2		6
Genco		2		3		5		5		2		-		4		1
Other		1		-		2		1		-		-		-		-
Ameren^(a)	$	27	$	18	$	57	$	40	$	2	$	6	$	11	$	12

(a)	Includes amounts for Ameren registrant and nonregistrant subsidiaries.

Ameren Illinois Company [Member]

Summary Of Benefit Plan Costs Incurred

	Pension Costs								Postretirement Costs
	Three Months				Six Months				Three Months				Six Months
	2012		2011		2012		2011		2012		2011		2012		2011
Ameren Missouri	$	16	$	12	$	32	$	26	$	-	$	2	$	5	$	5
Ameren Illinois		8		3		18		8		-		4		2		6
Genco		2		3		5		5		2		-		4		1
Other		1		-		2		1		-		-		-		-
Ameren^(a)	$	27	$	18	$	57	$	40	$	2	$	6	$	11	$	12

(a)	Includes amounts for Ameren registrant and nonregistrant subsidiaries.

Ameren Energy Generating Company [Member]

Summary Of Benefit Plan Costs Incurred

	Pension Costs								Postretirement Costs
	Three Months				Six Months				Three Months				Six Months
	2012		2011		2012		2011		2012		2011		2012		2011
Ameren Missouri	$	16	$	12	$	32	$	26	$	-	$	2	$	5	$	5
Ameren Illinois		8		3		18		8		-		4		2		6
Genco		2		3		5		5		2		-		4		1
Other		1		-		2		1		-		-		-		-
Ameren^(a)	$	27	$	18	$	57	$	40	$	2	$	6	$	11	$	12

(a)	Includes amounts for Ameren registrant and nonregistrant subsidiaries.

- Definition

Tabular disclosure of one or more of the entity's defined benefit pension plans or one or more other defined benefit postretirement plans, separately for pension plans and other postretirement benefit plans including the entity's schedule of fair value of plan assets for defined benefit or other postretirement plans.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 158

-Paragraph 4, 7, 16, 20, 21

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=21915506&loc=d3e2417-114920

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 55

-Paragraph 17

-URI http://asc.fasb.org/extlink&oid=21916443&loc=d3e4179-114921

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=21915506&loc=d3e1928-114920

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 5

-Subparagraph d

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=21915506&loc=d3e2410-114920

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=21915506&loc=d3e2439-114920

Reference 8: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 5, 6, 7

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details