Fair Value Measurements (Tables)

6 Months Ended

Jun. 30, 2012

Schedule of Valuation Process And Unobservable Inputs

		Fair Value				Valuation Technique(s)	Unobservable Input	Range [Weighted Average]
		Assets Liabilities
Level 3 Derivative asset and liability - commodity contracts(a):
Ameren(b)	Fuel oils	$	6	$	(2)	Discounted Cash Flow	Escalation rate(%)(c)	0.50 - 0.78 [.72]
							Counterparty credit risk(%)(d),(e)	0.12 - 4 [2]
							Ameren credit risk(%)(d),(e)	4 - 23 [9]
						Option model	Volatilities(%)(c)	23 - 33 [26]
	Power(f)		182		(192)	Option model	Volatilities(%)(d)	17 - 143 [34]
							Average bid/ask consensus peak and offpeak pricing - forwards/swaps ($/MWh)(d)	21 - 44 [36]
						Discounted Cash Flow	Average bid/ask consensus peak and offpeak pricing - forwards/swaps ($/MWh)(d)	18 - 51 [34]
							Estimated auction price for FTRs ($/MW)(c)	(672) - 7,200 [138]
							Nodal basis ($/MWh)(c)	(6) - (0.50) [(3)]
							Counterparty credit risk(%)(d),(e)	0.06 - 12 [4]
							Ameren credit risk(%)(d),(e)	4 - 5 [5]
						Fundamental energy production model	Estimated future gas prices ($/mmbtu)(c)	4 - 6 [5]
						Contract price allocation	Estimated renewable energy credit costs ($/credit)(c)	5 - 7 [6]
	Uranium		-		(1)	Discounted Cash Flow	Average bid/ask consensus pricing ($/pound)(c)	62 - 63 [62]
Ameren Missouri	Fuel oils	$	5	$	(2)	Discounted Cash Flow	Escalation rate(%)(c)	0.50 - 0.75 [.65]
							Counterparty credit risk(%)(d),(e)	0.12 - 2 [2]
							Ameren credit risk(%)(d),(e)	5
						Option model	Volatilities(%)(c)	23 - 33 [25]
	Power(f)		31		(5)	Option model	Volatilities(%)(d)	43 - 143 [76]
							Average bid/ask consensus peak and offpeak pricing - ($/MWh)(d)	24 - 32 [27]
						Discounted Cash Flow	Average bid/ask consensus peak and offpeak pricing - forwards/swaps ($/MWh)(d)	21 - 46 [25]
							Estimated auction price for FTRs ($/MW)(c)	(149) - 1,851 [140]
							Nodal basis ($/MWh)(c)	(3) - (0.48) [(2)]
							Counterparty credit risk(%)(d),(e)	0.42 - 12 [7]
							Ameren Missouri credit risk(%)(d),(e)	5
	Uranium		-		(1)	Discounted Cash Flow	Average bid/ask consensus pricing ($/pound)(c)	62 - 63 [62]
Ameren Illinois	Power(f)	$	-	$	(221)	Discounted Cash Flow	Average bid/ask consensus peak and offpeak pricing - forwards/swaps ($/MWh)(c)	19 - 45 [26]
							Nodal basis ($/MWh)(d)	(4) - (1) [(2)]
							Ameren Illinois credit risk (%)(d),(e)	5
						Fundamental energy production model	Estimated future gas prices ($/mmbtu)(c)	4 - 6 [5]
						Contract price allocation	Estimated renewable energy credit costs ($/credit)(c)	5 - 7 [6]
Genco	Fuel oils	$	1	$	-	Discounted Cash Flow	Escalation rate(c)	0.50 - 0.78 [0.71]
							Counterparty credit risk (%)(d),(e)	2
							Genco credit risk(%)(d),(e)	23
						Option model	Volatilities (%)(c)	23 - 33 [24]

(a) The derivative asset and liability balances are presented net of counterparty credit considerations.

(b) Includes amounts for Ameren registrant and nonregistrant subsidiaries and intercompany eliminations.

(c) Generally, significant increases (decreases) in this input in isolation would result in a significantly higher (lower) fair value measurement.

(d) Generally, significant increases (decreases) in this input in isolation would result in a significantly lower (higher) fair value measurement.

(e) Counterparty credit risk is only applied to derivative asset balances. Ameren, Ameren Missouri, Ameren Illinois, and Genco credit risk is only applied to derivative liability balances.

(f) Power valuations utilize visible third party pricing evaluated by month for peak and off-peak through 2015. Valuations beyond 2015 utilize fundamentally modeled pricing by month for peak and off-peak.

Schedule Of Fair Value Hierarchy Of Assets And Liabilities Measured At Fair Value On Recurring Basis

		Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Other Unobservable Inputs (Level 3)		Total
Assets:
Ameren(a)	Derivative assets - commodity contracts(b):
	Fuel oils	$	12	$	-	$	6	$	18
	Natural gas		5		5		-		10
	Power		-		17		182		199
	Total derivative assets - commodity contracts	$	17	$	22	$	188	$	227
	Nuclear Decommissioning Trust Fund(c):
	Cash and cash equivalents	$	4	$	-	$	-	$	4
	Equity securities:
	U.S. large capitalization		247		-		-		247
	Debt securities:
	Corporate bonds		-		43		-		43
	Municipal bonds		-		1		-		1
	U.S. treasury and agency securities		-		87		-		87
	Asset-backed securities		-		12		-		12
	Other		-		1		-		1
	Total Nuclear Decommissioning Trust Fund	$	251	$	144	$	-	$	395
	Total Ameren	$	268	$	166	$	188	$	622
Ameren	Derivative assets - commodity contracts(b):
Missouri	Fuel oils	$	7	$	-	$	5	$	12
	Natural gas		2		-		-		2
	Power		-		10		31		41
	Total derivative assets - commodity contracts	$	9	$	10	$	36	$	55
	Nuclear Decommissioning Trust Fund(c):
	Cash and cash equivalents	$	4	$	-	$	-	$	4
	Equity securities:
	U.S. large capitalization		247		-		-		247
	Debt securities:
	Corporate bonds		-		43		-		43
	Municipal bonds		-		1		-		1
	U.S. treasury and agency securities		-		87		-		87
	Asset-backed securities		-		12		-		12
	Other		-		1		-		1
	Total Nuclear Decommissioning Trust Fund	$	251	$	144	$	-	$	395
	Total Ameren Missouri	$	260	$	154	$	36	$	450
Ameren	Derivative assets - commodity contracts(b):
Illinois	Natural gas	$	-	$	2	$	-	$	2

		Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Other Unobservable Inputs (Level 3)		Total
Genco	Derivative assets - commodity contracts(b):
	Fuel oils	$	4	$	-	$	1	$	5
	Natural gas		2		3		-		5
	Total Genco	$	6	$	3	$	1	$	10
Liabilities:
Ameren(a)	Derivative liabilities - commodity contracts(b):
	Coal	$	10	$	-	$	-	$	10
	Fuel oils		9		-		2		11
	Natural gas		15		153		-		168
	Power		-		22		192		214
	Uranium		-		-		1		1
	Total Ameren	$	34	$	175	$	195	$	404
Ameren	Derivative liabilities - commodity contracts(b):
Missouri	Fuel oils		2		-		2		4
	Natural gas		11		12		-		23
	Power		-		12		5		17
	Uranium		-		-		1		1
	Total Ameren Missouri	$	13	$	24	$	8	$	45
Ameren	Derivative liabilities - commodity contracts(b):
Illinois	Natural gas	$	2	$	142	$	-	$	144
	Power		-		-		221		221
	Total Ameren Illinois	$	2	$	142	$	221	$	365
Genco	Derivative liabilities - commodity contracts(b):
	Coal	$	8	$	-	$	-	$	8
	Fuel oils		5		-		-		5
	Natural gas		1		-		-		1
	Total Genco	$	14	$	-	$	-	$	14

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

(b) The derivative asset and liability balances are presented net of counterparty credit considerations.

(c) Balance excludes $(9) million of receivables, payables, and accrued income, net.

The following table sets forth, by level within the fair value hierarchy, our assets and liabilities measured at fair value on a recurring basis as of December 31, 2011:

		Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Other Unobservable Inputs (Level 3)		Total
Assets:
Ameren(a)	Derivative assets - commodity contracts(b):
	Fuel oils	$	33	$	-	$	4	$	37
	Natural gas		4		-		2		6
	Power		-		2		193		195
	Total derivative assets - commodity contracts	$	37	$	2	$	199	$	238
	Nuclear Decommissioning Trust Fund(c):
	Cash and cash equivalents	$	3	$	-	$	-	$	3
	Equity securities:
	U.S. large capitalization		234		-		-		234
	Debt securities:
	Corporate bonds		-		44		-		44
	Municipal bonds		-		1		-		1
	U.S. treasury and agency securities		-		65		-		65
	Asset-backed securities		-		10		-		10
	Other		-		1		-		1
	Total Nuclear Decommissioning Trust Fund	$	237	$	121	$	-	$	358
	Total Ameren	$	274	$	123	$	199	$	596
Ameren	Derivative assets - commodity contracts(b):
Missouri	Fuel oils	$	20	$	-	$	3	$	23
	Natural gas		2		-		-		2
	Power		-		1		29		30
	Total derivative assets - commodity contracts	$	22	$	1	$	32	$	55

		Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Other Unobservable Inputs (Level 3)		Total
	Nuclear Decommissioning Trust Fund(c):
	Cash and cash equivalents	$	3	$	-	$	-	$	3
	Equity securities:
	U.S. large capitalization		234		-		-		234
	Debt securities:
	Corporate bonds		-		44		-		44
	Municipal bonds		-		1		-		1
	U.S. treasury and agency securities		-		65		-		65
	Asset-backed securities		-		10		-		10
	Other		-		1		-		1
	Total Nuclear Decommissioning Trust Fund	$	237	$	121	$	-	$	358
	Total Ameren Missouri	$	259	$	122	$	32	$	413
Ameren	Derivative assets - commodity contracts(b):
Illinois	Natural gas	$	-	$	-	$	2	$	2
	Power		-		-		77		77
	Total Ameren Illinois	$	-	$	-	$	79	$	79
Genco	Derivative assets - commodity contracts(b):
	Fuel oils	$	10	$	-	$	1	$	11
	Natural gas		2		-		-		2
	Total Genco	$	12	$	-	$	1	$	13
Liabilities:
Ameren(a)	Derivative liabilities - commodity contracts(b):
	Fuel oils	$	2	$	-	$	-	$	2
	Natural gas		22		-		176		198
	Power		-		2		78		80
	Uranium		-		-		1		1
	Total Ameren	$	24	$	2	$	255	$	281
Ameren	Derivative liabilities - commodity contracts(b):
Missouri	Fuel oils	$	1	$	-	$	-	$	1
	Natural gas		12		-		14		26
	Power		-		1		8		9
	Uranium		-		-		1		1
	Total Ameren Missouri	$	13	$	1	$	23	$	37
Ameren	Derivative liabilities - commodity contracts(b):
Illinois	Natural gas		7		-		162		169
	Power		-		-		217		217
	Total Ameren Illinois	$	7	$	-	$	379	$	386
Genco	Derivative liabilities - commodity contracts(b):
	Fuel oils	$	1	$	-	$	-	$	1
	Natural gas		2		-		-		2
	Total Genco	$	3	$	-	$	-	$	3

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

(b) The derivative asset and liability balances are presented net of counterparty credit considerations.

(c) Balance excludes $(1) million of receivables, payables, and accrued income, net.

Schedule Of Changes In The Fair Value Of Financial Assets And Liabilities Classified As Level 3 In The Fair Value Hierarchy

	Net derivative commodity contracts
Three Months	Ameren Missouri			Ameren Illinois			Genco			Other(c)			Ameren
Fuel oils:
Beginning balance at April 1, 2012	$	7		$	(a	)	$	2		$	-		$	9
Realized and unrealized gains (losses):
Included in earnings(b)		-			(a	)		(2	)		-			(2	)
Included in regulatory assets/liabilities		(4	)		(a	)		(a	)		(a	)		(4	)
Total realized and unrealized gains (losses)		(4	)		(a	)		(2	)		-			(6	)
Purchases		2			(a	)		1			-			3
Sales		(1	)		(a	)		-			-			(1	)
Settlements		(1	)		(a	)		-			-			(1	)
Ending balance at June 30, 2012	$	3		$	(a	)	$	1		$	-		$	4
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2012	$	(2	)	$	(a	)	$	-		$	-		$	(2	)

	Net derivative commodity contracts
Three Months	Ameren Missouri			Ameren Illinois			Genco			Other(c)			Ameren
Power:
Beginning balance at April 1, 2012	$	20		$	(284	)	$	-		$	240		$	(24	)
Realized and unrealized gains (losses):
Included in earnings(b)		-			-			-			(1	)		(1	)
Included in OCI		-			-			-			10			10
Included in regulatory assets/liabilities		(4	)		(1	)		(a	)		(5	)		(10	)
Total realized and unrealized gains (losses)		(4	)		(1	)		-			4			(1	)
Purchases		22			-			-			6			28
Sales		-			-			-			6			6
Settlements		(11	)		64			-			(73	)		(20	)
Transfers into Level 3		-			-			-			1			1
Transfers out of Level 3		(1	)		-			-			1			-
Ending balance at June 30, 2012	$	26		$	(221	)	$	-		$	185		$	(10	)
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2012	$	(1	)	$	(6	)	$	-		$	8		$	1
Uranium:
Beginning balance at April 1, 2012	$	(1	)	$	(a	)	$	(a	)	$	(a	)	$	(1	)
Realized and unrealized gains (losses):
Included in regulatory assets/liabilities		-			(a	)		(a	)		(a	)		-
Total realized and unrealized gains (losses)		-			(a	)		(a	)		(a	)		-
Ending balance at June 30, 2012	$	(1	)	$	(a	)	$	(a	)	$	(a	)	$	(1	)
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2012	$	-		$	(a	)	$	(a	)	$	(a	)	$	-

(a) Not applicable.

(b) Net gains and losses on fuel oils and natural gas derivative commodity contracts are recorded in “Operating Expenses - Fuel”, while net gains and losses on power derivative commodity contracts are recorded in “Operating Revenues - Electric”.

(c) Includes amounts for Merchant Generation nonregistrant subsidiaries and intercompany eliminations, including the elimination of financial power contracts between Ameren Illinois and Marketing Company.

The following table summarizes the changes in the fair value of financial assets and liabilities classified as Level 3 in the fair value hierarchy for the three months ended June 30, 2011:

	Net derivative commodity contracts
Three Months	Ameren Missouri			Ameren Illinois			Genco			Other(c)			Ameren
Fuel oils:
Beginning balance at April 1, 2011	$	57		$	(a	)	$	29		$	10		$	96
Realized and unrealized gains (losses):
Included in earnings(b)		-			(a	)		(3	)		(2	)		(5	)
Included in regulatory assets/liabilities		(9	)		(a	)		(a	)		(a	)		(9	)
Total realized and unrealized gains (losses)		(9	)		(a	)		(3	)		(2	)		(14	)
Purchases		1			(a	)		-			-			1
Settlements		(8	)		(a	)		(5	)		(2	)		(15	)
Ending balance at June 30, 2011	$	41		$	(a	)	$	21		$	6		$	68
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2011	$	(8	)	$	(a	)	$	(4	)	$	(2	)	$	(14	)
Natural gas:
Beginning balance at April 1, 2011	$	(12	)	$	(108	)	$	-		$	-		$	(120	)
Realized and unrealized gains (losses):
Included in regulatory assets/liabilities		(1	)		(19	)		(a	)		(a	)		(20	)
Total realized and unrealized gains (losses)		(1	)		(19	)		-			-			(20	)
Purchases		-			1			-			-			1
Settlements		2			20			-			-			22
Ending balance at June 30, 2011	$	(11	)	$	(106	)	$	-		$	-		$	(117	)
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2011	$	(1	)	$	(17	)	$	-		$	-		$	(18	)
Power:
Beginning balance at April 1, 2011	$	2		$	(325	)	$	3		$	351		$	31
Realized and unrealized gains (losses):
Included in earnings(b)		-			-			(1	)		(14	)		(15	)
Included in OCI		-			-			-			5			5
Included in regulatory assets/liabilities		(1	)		77			(a	)		(10	)		66
Total realized and unrealized gains (losses)		(1	)		77			(1	)		(19	)		56

	Net derivative commodity contracts
Three Months	Ameren Missouri			Ameren Illinois			Genco			Other(c)			Ameren
Purchases	$	29		$	-		$	-		$	21		$	50
Sales		-			-			-			(7	)		(7	)
Settlements		(6	)		44			(1	)		(53	)		(16	)
Transfers into Level 3		-			-			-			1			1
Transfers out of Level 3		1			-			-			1			2
Ending balance at June 30, 2011	$	25		$	(204	)	$	1		$	295		$	117
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2011	$	(1	)	$	68		$	(1	)	$	(7	)	$	59
Uranium:
Beginning balance at April 1, 2011	$	1		$	(a	)	$	(a	)	$	(a	)	$	1
Realized and unrealized gains (losses):
Included in regulatory assets/liabilities		(3	)		(a	)		(a	)		(a	)		(3	)
Total realized and unrealized gains (losses)		(3	)		(a	)		(a	)		(a	)		(3	)
Ending balance at June 30, 2011	$	(2	)	$	(a	)	$	(a	)	$	(a	)	$	(2	)
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2011	$	(2	)	$	(a	)	$	(a	)	$	(a	)	$	(2	)

(a) Not applicable.

(b) Net gains and losses on fuel oils and natural gas derivative commodity contracts are recorded in Operating Expenses - Fuel, while net gains and losses on power derivative commodity contracts are recorded in Operating Revenues - Electric.

(c) Includes amounts for Merchant Generation nonregistrant subsidiaries and intercompany eliminations, including the elimination of financial power contracts between Ameren Illinois and Marketing Company.

The following table summarizes the changes in the fair value of financial assets and liabilities classified as Level 3 in the fair value hierarchy for the six months ended June 30, 2012:

	Net derivative commodity contracts
Six Months	Ameren Missouri			Ameren Illinois			Genco			Other(c)			Ameren
Fuel oils:
Beginning balance at January 1, 2012	$	3		$	(a	)	$	1		$	-		$	4
Realized and unrealized gains (losses):
Included in earnings(b)		-			(a	)		-			-			-
Included in regulatory assets/liabilities		(2	)		(a	)		(a	)		(a	)		(2	)
Total realized and unrealized gains (losses)		(2	)		(a	)		-			-			(2	)
Purchases		2			(a	)		1			-			3
Sales		(1	)		(a	)		-			-			(1	)
Settlements		(1	)		(a	)		-			-			(1	)
Transfers into Level 3		2			(a	)		-			-			2
Transfers out of Level 3		-			(a	)		(1	)		-			(1	)
Ending balance at June 30, 2012	$	3		$	(a	)	$	1		$	-		$	4
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2012	$	(1	)	$	(a	)	$	-		$	-		$	(1	)
Natural gas:
Beginning balance at January 1, 2012	$	(14	)	$	(160	)	$	-		$	-		$	(174	)
Realized and unrealized gains (losses):
Included in regulatory assets/liabilities		(2	)		(26	)		(a	)		(a	)		(28	)
Total realized and unrealized gains (losses)		(2	)		(26	)		-			-			(28	)
Settlements		1			16			-			-			17
Transfer out of Level 3		15			170			-			-			185
Ending balance at June 30, 2012	$	-		$	-		$	-		$	-		$	-
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2012	$	9		$	114		$	-		$	-		$	123
Power:
Beginning balance at January 1, 2012	$	21		$	(140	)	$	-		$	234		$	115
Realized and unrealized gains (losses):
Included in earnings(b)		-			-			-			7			7
Included in OCI		-			-			-			34			34
Included in regulatory assets/liabilities		9			(221	)		(a	)		44			(168	)
Total realized and unrealized gains (losses)		9			(221	)		-			85			(127	)
Purchases		22			-			-			5			27
Sales		-			-			-			7			7
Settlements		(24	)		140			-			(150	)		(34	)
Transfers into Level 3		-			-			-			1			1

	Net derivative commodity contracts
Six Months	Ameren Missouri			Ameren Illinois			Genco			Other(c)			Ameren
Transfers out of Level 3		(2	)		-			-			3			1
Ending balance at June 30, 2012	$	26		$	(221	)	$	-		$	185		$	(10	)
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2012	$	3		$	(195	)(d)	$	-		$	42		$	(150	)
Uranium:
Beginning balance at January 1, 2012	$	(1	)	$	(a	)	$	(a	)	$	(a	)	$	(1	)
Realized and unrealized gains (losses):
Included in regulatory assets/liabilities		-			(a	)		(a	)		(a	)		-
Total realized and unrealized gains (losses)		-			(a	)		(a	)		(a	)		-
Ending balance at June 30, 2012	$	(1	)	$	(a	)	$	(a	)	$	(a	)	$	(1	)
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2012	$	-		$	(a	)	$	(a	)	$	(a	)	$	-

(a) Not applicable.

(b) Net gains and losses on fuel oils and natural gas derivative commodity contracts are recorded in “Operating Expenses - Fuel”, while net gains and losses on power derivative commodity contracts are recorded in “Operating Revenues - Electric”.

(c) Includes amounts for Merchant Generation nonregistrant subsidiaries and intercompany eliminations, including the elimination of financial power contracts between Ameren Illinois and Marketing Company.

(d) The change in unrealized losses was due to decreases in long-term power prices applied to 20-year Ameren Illinois’ swap contracts, which expire in May 2032.

The following table summarizes the changes in the fair value of financial assets and liabilities classified as Level 3 in the fair value hierarchy for the six months ended June 30, 2011:

	Net derivative commodity contracts
Six Months	Ameren Missouri			Ameren Illinois			Genco			Other(c)			Ameren
Fuel oils:
Beginning balance at January 1, 2011	$	30		$	(a	)	$	17		$	4		$	51
Realized and unrealized gains (losses):
Included in earnings(b)		-			(a	)		12			5			17
Included in regulatory assets/liabilities		22			(a	)		(a	)		(a	)		22
Total realized and unrealized gains (losses)		22			(a	)		12			5			39
Purchases		2			(a	)		-			-			2
Settlements		(13	)		(a	)		(8	)		(3	)		(24	)
Ending balance at June 30, 2011	$	41		$	(a	)	$	21		$	6		$	68
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2011	$	18		$	(a	)	$	9		$	3		$	30
Natural gas:
Beginning balance at January 1, 2011	$	(14	)	$	(134	)	$	-		$	-		$	(148	)
Realized and unrealized gains (losses):
Included in regulatory assets/liabilities		(1	)		(12	)		(a	)		(a	)		(13	)
Total realized and unrealized gains (losses)		(1	)		(12	)		-			-			(13	)
Purchases		-			1			-			-			1
Settlements		4			39			-			-			43
Ending balance at June 30, 2011	$	(11	)	$	(106	)	$	-		$	-		$	(117	)
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2011	$	1		$	8		$	-		$	-		$	9
Power:
Beginning balance at January 1, 2011	$	2		$	(352	)	$	3		$	383		$	36
Realized and unrealized gains (losses):
Included in earnings(b)		-			-			(1	)		(17	)		(18	)
Included in OCI		-			-			-			5			5
Included in regulatory assets/liabilities		6			47			(a	)		11			64
Total realized and unrealized gains (losses)		6			47			(1	)		(1	)		51
Purchases		29			-			-			30			59
Sales		-			-			-			(16	)		(16	)
Settlements		(12	)		101			(1	)		(104	)		(16	)
Transfers into Level 3		(1	)		-			-			2			1
Transfers out of Level 3		1			-			-			1			2
Ending balance at June 30, 2011	$	25		$	(204	)	$	1		$	295		$	117
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2011	$	-		$	64		$	(1	)	$	(4	)	$	59

	Net derivative commodity contracts
Six Months	Ameren Missouri			Ameren Illinois			Genco			Other(c)			Ameren
Uranium:
Beginning balance at January 1, 2011	$	2		$	(a	)	$	(a	)	$	(a	)	$	2
Realized and unrealized gains (losses):
Included in regulatory assets/liabilities		(4	)		(a	)		(a	)		(a	)		(4	)
Total realized and unrealized gains (losses)		(4	)		(a	)		(a	)		(a	)		(4	)
Ending balance at June 30, 2011	$	(2	)	$	(a	)	$	(a	)	$	(a	)	$	(2	)
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2011	$	(2	)	$	(a	)	$	(a	)	$	(a	)	$	(2	)

(a) Not applicable.

(b) Net gains and losses on fuel oils and natural gas derivative commodity contracts are recorded in Operating Expenses - Fuel, while net gains and losses on power derivative commodity contracts are recorded in Operating Revenues - Electric.

(c) Includes amounts for Merchant Generation nonregistrant subsidiaries and intercompany eliminations, including the elimination of financial power contracts between Ameren Illinois and Marketing Company.

Schedule Of Transfers Between Fair Value Hierarchy Levels

	Three Months					Six Months
	2012			2011		2012			2011
Ameren - derivative commodity contracts:(a)
Transfers into Level 3 / Transfers out of Level 1 - Fuel oils	$	-		$	-	$	2		$	-
Transfers out of Level 3 / Transfers into Level 1 - Fuel oils		-			-		(1	)		-
Transfers out of Level 3 / Transfers into Level 2 - Natural gas		-			-		185			-
Transfers into Level 3 / Transfers out of Level 2 - Power		1			1		1			1
Transfers out of Level 3 / Transfers into Level 2 - Power		-			2		1			2
Net fair value of Level 3 transfers	$	1		$	3	$	188		$	3
Ameren Missouri - derivative commodity contracts:
Transfers into Level 3 / Transfers out of Level 1 - Fuel oils	$	-		$	-	$	2		$	-
Transfers out of Level 3 / Transfers into Level 2 - Natural gas		-			-		15			-
Transfers into Level 3 / Transfers out of Level 2 - Power		-			-		-			(1	)
Transfers out of Level 3 / Transfers into Level 2 - Power		(1	)		1		(2	)		1
Net fair value of Level 3 transfers	$	(1	)	$	1	$	15		$	-
Ameren Illinois - derivative commodity contracts:
Transfers out of Level 3 / Transfers into Level 2 - Natural gas	$	-		$	-	$	170		$	-
Genco - derivative commodity contracts:
Transfers out of Level 3 / Transfers into Level 1 - Fuel oils	$	-		$	-	$	(1	)	$	-

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

Schedule Of Carrying Amounts And Estimated Fair Values Of Long-Term Debt, Capital Lease Obligations And Preferred Stock

	June 30, 2012				December 31, 2011
	Carrying Amount		Fair Value		Carrying Amount		Fair Value
Ameren:(a)(b)
Long-term debt and capital lease obligations (including current portion)	$	6,857	$	7,766	$	6,856	$	7,800
Preferred stock		142		93		142		92
Ameren Missouri:
Long-term debt and capital lease obligations (including current portion)	$	3,950	$	4,619	$	3,950	$	4,541
Preferred stock		80		55		80		55
Ameren Illinois:
Long-term debt (including current portion)	$	1,658	$	1,984	$	1,658	$	1,943
Preferred stock		62		38		62		37
Genco:
Long-term debt (including current portion)	$	824	$	679	$	824	$	839

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

(b) Preferred stock not subject to mandatory redemption of the Ameren subsidiaries along with the 20% noncontrolling interest of EEI is recorded in Noncontrolling Interests on the balance sheet.

Ameren Missouri [Member]

Schedule of Valuation Process And Unobservable Inputs

		Fair Value				Valuation Technique(s)	Unobservable Input	Range [Weighted Average]
		Assets Liabilities
Level 3 Derivative asset and liability - commodity contracts(a):
Ameren(b)	Fuel oils	$	6	$	(2)	Discounted Cash Flow	Escalation rate(%)(c)	0.50 - 0.78 [.72]
							Counterparty credit risk(%)(d),(e)	0.12 - 4 [2]
							Ameren credit risk(%)(d),(e)	4 - 23 [9]
						Option model	Volatilities(%)(c)	23 - 33 [26]
	Power(f)		182		(192)	Option model	Volatilities(%)(d)	17 - 143 [34]
							Average bid/ask consensus peak and offpeak pricing - forwards/swaps ($/MWh)(d)	21 - 44 [36]
						Discounted Cash Flow	Average bid/ask consensus peak and offpeak pricing - forwards/swaps ($/MWh)(d)	18 - 51 [34]
							Estimated auction price for FTRs ($/MW)(c)	(672) - 7,200 [138]
							Nodal basis ($/MWh)(c)	(6) - (0.50) [(3)]
							Counterparty credit risk(%)(d),(e)	0.06 - 12 [4]
							Ameren credit risk(%)(d),(e)	4 - 5 [5]
						Fundamental energy production model	Estimated future gas prices ($/mmbtu)(c)	4 - 6 [5]
						Contract price allocation	Estimated renewable energy credit costs ($/credit)(c)	5 - 7 [6]
	Uranium		-		(1)	Discounted Cash Flow	Average bid/ask consensus pricing ($/pound)(c)	62 - 63 [62]
Ameren Missouri	Fuel oils	$	5	$	(2)	Discounted Cash Flow	Escalation rate(%)(c)	0.50 - 0.75 [.65]
							Counterparty credit risk(%)(d),(e)	0.12 - 2 [2]
							Ameren credit risk(%)(d),(e)	5
						Option model	Volatilities(%)(c)	23 - 33 [25]
	Power(f)		31		(5)	Option model	Volatilities(%)(d)	43 - 143 [76]
							Average bid/ask consensus peak and offpeak pricing - ($/MWh)(d)	24 - 32 [27]
						Discounted Cash Flow	Average bid/ask consensus peak and offpeak pricing - forwards/swaps ($/MWh)(d)	21 - 46 [25]
							Estimated auction price for FTRs ($/MW)(c)	(149) - 1,851 [140]
							Nodal basis ($/MWh)(c)	(3) - (0.48) [(2)]
							Counterparty credit risk(%)(d),(e)	0.42 - 12 [7]
							Ameren Missouri credit risk(%)(d),(e)	5
	Uranium		-		(1)	Discounted Cash Flow	Average bid/ask consensus pricing ($/pound)(c)	62 - 63 [62]
Ameren Illinois	Power(f)	$	-	$	(221)	Discounted Cash Flow	Average bid/ask consensus peak and offpeak pricing - forwards/swaps ($/MWh)(c)	19 - 45 [26]
							Nodal basis ($/MWh)(d)	(4) - (1) [(2)]
							Ameren Illinois credit risk (%)(d),(e)	5
						Fundamental energy production model	Estimated future gas prices ($/mmbtu)(c)	4 - 6 [5]
						Contract price allocation	Estimated renewable energy credit costs ($/credit)(c)	5 - 7 [6]
Genco	Fuel oils	$	1	$	-	Discounted Cash Flow	Escalation rate(c)	0.50 - 0.78 [0.71]
							Counterparty credit risk (%)(d),(e)	2
							Genco credit risk(%)(d),(e)	23
						Option model	Volatilities (%)(c)	23 - 33 [24]

(a) The derivative asset and liability balances are presented net of counterparty credit considerations.

(b) Includes amounts for Ameren registrant and nonregistrant subsidiaries and intercompany eliminations.

(c) Generally, significant increases (decreases) in this input in isolation would result in a significantly higher (lower) fair value measurement.

(d) Generally, significant increases (decreases) in this input in isolation would result in a significantly lower (higher) fair value measurement.

(e) Counterparty credit risk is only applied to derivative asset balances. Ameren, Ameren Missouri, Ameren Illinois, and Genco credit risk is only applied to derivative liability balances.

(f) Power valuations utilize visible third party pricing evaluated by month for peak and off-peak through 2015. Valuations beyond 2015 utilize fundamentally modeled pricing by month for peak and off-peak.

Schedule Of Fair Value Hierarchy Of Assets And Liabilities Measured At Fair Value On Recurring Basis

		Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Other Unobservable Inputs (Level 3)		Total
Assets:
Ameren(a)	Derivative assets - commodity contracts(b):
	Fuel oils	$	12	$	-	$	6	$	18
	Natural gas		5		5		-		10
	Power		-		17		182		199
	Total derivative assets - commodity contracts	$	17	$	22	$	188	$	227
	Nuclear Decommissioning Trust Fund(c):
	Cash and cash equivalents	$	4	$	-	$	-	$	4
	Equity securities:
	U.S. large capitalization		247		-		-		247
	Debt securities:
	Corporate bonds		-		43		-		43
	Municipal bonds		-		1		-		1
	U.S. treasury and agency securities		-		87		-		87
	Asset-backed securities		-		12		-		12
	Other		-		1		-		1
	Total Nuclear Decommissioning Trust Fund	$	251	$	144	$	-	$	395
	Total Ameren	$	268	$	166	$	188	$	622
Ameren	Derivative assets - commodity contracts(b):
Missouri	Fuel oils	$	7	$	-	$	5	$	12
	Natural gas		2		-		-		2
	Power		-		10		31		41
	Total derivative assets - commodity contracts	$	9	$	10	$	36	$	55
	Nuclear Decommissioning Trust Fund(c):
	Cash and cash equivalents	$	4	$	-	$	-	$	4
	Equity securities:
	U.S. large capitalization		247		-		-		247
	Debt securities:
	Corporate bonds		-		43		-		43
	Municipal bonds		-		1		-		1
	U.S. treasury and agency securities		-		87		-		87
	Asset-backed securities		-		12		-		12
	Other		-		1		-		1
	Total Nuclear Decommissioning Trust Fund	$	251	$	144	$	-	$	395
	Total Ameren Missouri	$	260	$	154	$	36	$	450
Ameren	Derivative assets - commodity contracts(b):
Illinois	Natural gas	$	-	$	2	$	-	$	2

		Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Other Unobservable Inputs (Level 3)		Total
Genco	Derivative assets - commodity contracts(b):
	Fuel oils	$	4	$	-	$	1	$	5
	Natural gas		2		3		-		5
	Total Genco	$	6	$	3	$	1	$	10
Liabilities:
Ameren(a)	Derivative liabilities - commodity contracts(b):
	Coal	$	10	$	-	$	-	$	10
	Fuel oils		9		-		2		11
	Natural gas		15		153		-		168
	Power		-		22		192		214
	Uranium		-		-		1		1
	Total Ameren	$	34	$	175	$	195	$	404
Ameren	Derivative liabilities - commodity contracts(b):
Missouri	Fuel oils		2		-		2		4
	Natural gas		11		12		-		23
	Power		-		12		5		17
	Uranium		-		-		1		1
	Total Ameren Missouri	$	13	$	24	$	8	$	45
Ameren	Derivative liabilities - commodity contracts(b):
Illinois	Natural gas	$	2	$	142	$	-	$	144
	Power		-		-		221		221
	Total Ameren Illinois	$	2	$	142	$	221	$	365
Genco	Derivative liabilities - commodity contracts(b):
	Coal	$	8	$	-	$	-	$	8
	Fuel oils		5		-		-		5
	Natural gas		1		-		-		1
	Total Genco	$	14	$	-	$	-	$	14

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

(b) The derivative asset and liability balances are presented net of counterparty credit considerations.

(c) Balance excludes $(9) million of receivables, payables, and accrued income, net.

The following table sets forth, by level within the fair value hierarchy, our assets and liabilities measured at fair value on a recurring basis as of December 31, 2011:

		Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Other Unobservable Inputs (Level 3)		Total
Assets:
Ameren(a)	Derivative assets - commodity contracts(b):
	Fuel oils	$	33	$	-	$	4	$	37
	Natural gas		4		-		2		6
	Power		-		2		193		195
	Total derivative assets - commodity contracts	$	37	$	2	$	199	$	238
	Nuclear Decommissioning Trust Fund(c):
	Cash and cash equivalents	$	3	$	-	$	-	$	3
	Equity securities:
	U.S. large capitalization		234		-		-		234
	Debt securities:
	Corporate bonds		-		44		-		44
	Municipal bonds		-		1		-		1
	U.S. treasury and agency securities		-		65		-		65
	Asset-backed securities		-		10		-		10
	Other		-		1		-		1
	Total Nuclear Decommissioning Trust Fund	$	237	$	121	$	-	$	358
	Total Ameren	$	274	$	123	$	199	$	596
Ameren	Derivative assets - commodity contracts(b):
Missouri	Fuel oils	$	20	$	-	$	3	$	23
	Natural gas		2		-		-		2
	Power		-		1		29		30
	Total derivative assets - commodity contracts	$	22	$	1	$	32	$	55

		Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Other Unobservable Inputs (Level 3)		Total
	Nuclear Decommissioning Trust Fund(c):
	Cash and cash equivalents	$	3	$	-	$	-	$	3
	Equity securities:
	U.S. large capitalization		234		-		-		234
	Debt securities:
	Corporate bonds		-		44		-		44
	Municipal bonds		-		1		-		1
	U.S. treasury and agency securities		-		65		-		65
	Asset-backed securities		-		10		-		10
	Other		-		1		-		1
	Total Nuclear Decommissioning Trust Fund	$	237	$	121	$	-	$	358
	Total Ameren Missouri	$	259	$	122	$	32	$	413
Ameren	Derivative assets - commodity contracts(b):
Illinois	Natural gas	$	-	$	-	$	2	$	2
	Power		-		-		77		77
	Total Ameren Illinois	$	-	$	-	$	79	$	79
Genco	Derivative assets - commodity contracts(b):
	Fuel oils	$	10	$	-	$	1	$	11
	Natural gas		2		-		-		2
	Total Genco	$	12	$	-	$	1	$	13
Liabilities:
Ameren(a)	Derivative liabilities - commodity contracts(b):
	Fuel oils	$	2	$	-	$	-	$	2
	Natural gas		22		-		176		198
	Power		-		2		78		80
	Uranium		-		-		1		1
	Total Ameren	$	24	$	2	$	255	$	281
Ameren	Derivative liabilities - commodity contracts(b):
Missouri	Fuel oils	$	1	$	-	$	-	$	1
	Natural gas		12		-		14		26
	Power		-		1		8		9
	Uranium		-		-		1		1
	Total Ameren Missouri	$	13	$	1	$	23	$	37
Ameren	Derivative liabilities - commodity contracts(b):
Illinois	Natural gas		7		-		162		169
	Power		-		-		217		217
	Total Ameren Illinois	$	7	$	-	$	379	$	386
Genco	Derivative liabilities - commodity contracts(b):
	Fuel oils	$	1	$	-	$	-	$	1
	Natural gas		2		-		-		2
	Total Genco	$	3	$	-	$	-	$	3

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

(b) The derivative asset and liability balances are presented net of counterparty credit considerations.

(c) Balance excludes $(1) million of receivables, payables, and accrued income, net.

Schedule Of Changes In The Fair Value Of Financial Assets And Liabilities Classified As Level 3 In The Fair Value Hierarchy

	Net derivative commodity contracts
Three Months	Ameren Missouri			Ameren Illinois			Genco			Other(c)			Ameren
Fuel oils:
Beginning balance at April 1, 2012	$	7		$	(a	)	$	2		$	-		$	9
Realized and unrealized gains (losses):
Included in earnings(b)		-			(a	)		(2	)		-			(2	)
Included in regulatory assets/liabilities		(4	)		(a	)		(a	)		(a	)		(4	)
Total realized and unrealized gains (losses)		(4	)		(a	)		(2	)		-			(6	)
Purchases		2			(a	)		1			-			3
Sales		(1	)		(a	)		-			-			(1	)
Settlements		(1	)		(a	)		-			-			(1	)
Ending balance at June 30, 2012	$	3		$	(a	)	$	1		$	-		$	4
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2012	$	(2	)	$	(a	)	$	-		$	-		$	(2	)

	Net derivative commodity contracts
Three Months	Ameren Missouri			Ameren Illinois			Genco			Other(c)			Ameren
Power:
Beginning balance at April 1, 2012	$	20		$	(284	)	$	-		$	240		$	(24	)
Realized and unrealized gains (losses):
Included in earnings(b)		-			-			-			(1	)		(1	)
Included in OCI		-			-			-			10			10
Included in regulatory assets/liabilities		(4	)		(1	)		(a	)		(5	)		(10	)
Total realized and unrealized gains (losses)		(4	)		(1	)		-			4			(1	)
Purchases		22			-			-			6			28
Sales		-			-			-			6			6
Settlements		(11	)		64			-			(73	)		(20	)
Transfers into Level 3		-			-			-			1			1
Transfers out of Level 3		(1	)		-			-			1			-
Ending balance at June 30, 2012	$	26		$	(221	)	$	-		$	185		$	(10	)
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2012	$	(1	)	$	(6	)	$	-		$	8		$	1
Uranium:
Beginning balance at April 1, 2012	$	(1	)	$	(a	)	$	(a	)	$	(a	)	$	(1	)
Realized and unrealized gains (losses):
Included in regulatory assets/liabilities		-			(a	)		(a	)		(a	)		-
Total realized and unrealized gains (losses)		-			(a	)		(a	)		(a	)		-
Ending balance at June 30, 2012	$	(1	)	$	(a	)	$	(a	)	$	(a	)	$	(1	)
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2012	$	-		$	(a	)	$	(a	)	$	(a	)	$	-

(a) Not applicable.

(b) Net gains and losses on fuel oils and natural gas derivative commodity contracts are recorded in “Operating Expenses - Fuel”, while net gains and losses on power derivative commodity contracts are recorded in “Operating Revenues - Electric”.

(c) Includes amounts for Merchant Generation nonregistrant subsidiaries and intercompany eliminations, including the elimination of financial power contracts between Ameren Illinois and Marketing Company.

The following table summarizes the changes in the fair value of financial assets and liabilities classified as Level 3 in the fair value hierarchy for the three months ended June 30, 2011:

	Net derivative commodity contracts
Three Months	Ameren Missouri			Ameren Illinois			Genco			Other(c)			Ameren
Fuel oils:
Beginning balance at April 1, 2011	$	57		$	(a	)	$	29		$	10		$	96
Realized and unrealized gains (losses):
Included in earnings(b)		-			(a	)		(3	)		(2	)		(5	)
Included in regulatory assets/liabilities		(9	)		(a	)		(a	)		(a	)		(9	)
Total realized and unrealized gains (losses)		(9	)		(a	)		(3	)		(2	)		(14	)
Purchases		1			(a	)		-			-			1
Settlements		(8	)		(a	)		(5	)		(2	)		(15	)
Ending balance at June 30, 2011	$	41		$	(a	)	$	21		$	6		$	68
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2011	$	(8	)	$	(a	)	$	(4	)	$	(2	)	$	(14	)
Natural gas:
Beginning balance at April 1, 2011	$	(12	)	$	(108	)	$	-		$	-		$	(120	)
Realized and unrealized gains (losses):
Included in regulatory assets/liabilities		(1	)		(19	)		(a	)		(a	)		(20	)
Total realized and unrealized gains (losses)		(1	)		(19	)		-			-			(20	)
Purchases		-			1			-			-			1
Settlements		2			20			-			-			22
Ending balance at June 30, 2011	$	(11	)	$	(106	)	$	-		$	-		$	(117	)
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2011	$	(1	)	$	(17	)	$	-		$	-		$	(18	)
Power:
Beginning balance at April 1, 2011	$	2		$	(325	)	$	3		$	351		$	31
Realized and unrealized gains (losses):
Included in earnings(b)		-			-			(1	)		(14	)		(15	)
Included in OCI		-			-			-			5			5
Included in regulatory assets/liabilities		(1	)		77			(a	)		(10	)		66
Total realized and unrealized gains (losses)		(1	)		77			(1	)		(19	)		56

	Net derivative commodity contracts
Three Months	Ameren Missouri			Ameren Illinois			Genco			Other(c)			Ameren
Purchases	$	29		$	-		$	-		$	21		$	50
Sales		-			-			-			(7	)		(7	)
Settlements		(6	)		44			(1	)		(53	)		(16	)
Transfers into Level 3		-			-			-			1			1
Transfers out of Level 3		1			-			-			1			2
Ending balance at June 30, 2011	$	25		$	(204	)	$	1		$	295		$	117
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2011	$	(1	)	$	68		$	(1	)	$	(7	)	$	59
Uranium:
Beginning balance at April 1, 2011	$	1		$	(a	)	$	(a	)	$	(a	)	$	1
Realized and unrealized gains (losses):
Included in regulatory assets/liabilities		(3	)		(a	)		(a	)		(a	)		(3	)
Total realized and unrealized gains (losses)		(3	)		(a	)		(a	)		(a	)		(3	)
Ending balance at June 30, 2011	$	(2	)	$	(a	)	$	(a	)	$	(a	)	$	(2	)
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2011	$	(2	)	$	(a	)	$	(a	)	$	(a	)	$	(2	)

(a) Not applicable.

(b) Net gains and losses on fuel oils and natural gas derivative commodity contracts are recorded in Operating Expenses - Fuel, while net gains and losses on power derivative commodity contracts are recorded in Operating Revenues - Electric.

(c) Includes amounts for Merchant Generation nonregistrant subsidiaries and intercompany eliminations, including the elimination of financial power contracts between Ameren Illinois and Marketing Company.

The following table summarizes the changes in the fair value of financial assets and liabilities classified as Level 3 in the fair value hierarchy for the six months ended June 30, 2012:

	Net derivative commodity contracts
Six Months	Ameren Missouri			Ameren Illinois			Genco			Other(c)			Ameren
Fuel oils:
Beginning balance at January 1, 2012	$	3		$	(a	)	$	1		$	-		$	4
Realized and unrealized gains (losses):
Included in earnings(b)		-			(a	)		-			-			-
Included in regulatory assets/liabilities		(2	)		(a	)		(a	)		(a	)		(2	)
Total realized and unrealized gains (losses)		(2	)		(a	)		-			-			(2	)
Purchases		2			(a	)		1			-			3
Sales		(1	)		(a	)		-			-			(1	)
Settlements		(1	)		(a	)		-			-			(1	)
Transfers into Level 3		2			(a	)		-			-			2
Transfers out of Level 3		-			(a	)		(1	)		-			(1	)
Ending balance at June 30, 2012	$	3		$	(a	)	$	1		$	-		$	4
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2012	$	(1	)	$	(a	)	$	-		$	-		$	(1	)
Natural gas:
Beginning balance at January 1, 2012	$	(14	)	$	(160	)	$	-		$	-		$	(174	)
Realized and unrealized gains (losses):
Included in regulatory assets/liabilities		(2	)		(26	)		(a	)		(a	)		(28	)
Total realized and unrealized gains (losses)		(2	)		(26	)		-			-			(28	)
Settlements		1			16			-			-			17
Transfer out of Level 3		15			170			-			-			185
Ending balance at June 30, 2012	$	-		$	-		$	-		$	-		$	-
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2012	$	9		$	114		$	-		$	-		$	123
Power:
Beginning balance at January 1, 2012	$	21		$	(140	)	$	-		$	234		$	115
Realized and unrealized gains (losses):
Included in earnings(b)		-			-			-			7			7
Included in OCI		-			-			-			34			34
Included in regulatory assets/liabilities		9			(221	)		(a	)		44			(168	)
Total realized and unrealized gains (losses)		9			(221	)		-			85			(127	)
Purchases		22			-			-			5			27
Sales		-			-			-			7			7
Settlements		(24	)		140			-			(150	)		(34	)
Transfers into Level 3		-			-			-			1			1

	Net derivative commodity contracts
Six Months	Ameren Missouri			Ameren Illinois			Genco			Other(c)			Ameren
Transfers out of Level 3		(2	)		-			-			3			1
Ending balance at June 30, 2012	$	26		$	(221	)	$	-		$	185		$	(10	)
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2012	$	3		$	(195	)(d)	$	-		$	42		$	(150	)
Uranium:
Beginning balance at January 1, 2012	$	(1	)	$	(a	)	$	(a	)	$	(a	)	$	(1	)
Realized and unrealized gains (losses):
Included in regulatory assets/liabilities		-			(a	)		(a	)		(a	)		-
Total realized and unrealized gains (losses)		-			(a	)		(a	)		(a	)		-
Ending balance at June 30, 2012	$	(1	)	$	(a	)	$	(a	)	$	(a	)	$	(1	)
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2012	$	-		$	(a	)	$	(a	)	$	(a	)	$	-

(a) Not applicable.

(b) Net gains and losses on fuel oils and natural gas derivative commodity contracts are recorded in “Operating Expenses - Fuel”, while net gains and losses on power derivative commodity contracts are recorded in “Operating Revenues - Electric”.

(c) Includes amounts for Merchant Generation nonregistrant subsidiaries and intercompany eliminations, including the elimination of financial power contracts between Ameren Illinois and Marketing Company.

(d) The change in unrealized losses was due to decreases in long-term power prices applied to 20-year Ameren Illinois’ swap contracts, which expire in May 2032.

The following table summarizes the changes in the fair value of financial assets and liabilities classified as Level 3 in the fair value hierarchy for the six months ended June 30, 2011:

	Net derivative commodity contracts
Six Months	Ameren Missouri			Ameren Illinois			Genco			Other(c)			Ameren
Fuel oils:
Beginning balance at January 1, 2011	$	30		$	(a	)	$	17		$	4		$	51
Realized and unrealized gains (losses):
Included in earnings(b)		-			(a	)		12			5			17
Included in regulatory assets/liabilities		22			(a	)		(a	)		(a	)		22
Total realized and unrealized gains (losses)		22			(a	)		12			5			39
Purchases		2			(a	)		-			-			2
Settlements		(13	)		(a	)		(8	)		(3	)		(24	)
Ending balance at June 30, 2011	$	41		$	(a	)	$	21		$	6		$	68
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2011	$	18		$	(a	)	$	9		$	3		$	30
Natural gas:
Beginning balance at January 1, 2011	$	(14	)	$	(134	)	$	-		$	-		$	(148	)
Realized and unrealized gains (losses):
Included in regulatory assets/liabilities		(1	)		(12	)		(a	)		(a	)		(13	)
Total realized and unrealized gains (losses)		(1	)		(12	)		-			-			(13	)
Purchases		-			1			-			-			1
Settlements		4			39			-			-			43
Ending balance at June 30, 2011	$	(11	)	$	(106	)	$	-		$	-		$	(117	)
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2011	$	1		$	8		$	-		$	-		$	9
Power:
Beginning balance at January 1, 2011	$	2		$	(352	)	$	3		$	383		$	36
Realized and unrealized gains (losses):
Included in earnings(b)		-			-			(1	)		(17	)		(18	)
Included in OCI		-			-			-			5			5
Included in regulatory assets/liabilities		6			47			(a	)		11			64
Total realized and unrealized gains (losses)		6			47			(1	)		(1	)		51
Purchases		29			-			-			30			59
Sales		-			-			-			(16	)		(16	)
Settlements		(12	)		101			(1	)		(104	)		(16	)
Transfers into Level 3		(1	)		-			-			2			1
Transfers out of Level 3		1			-			-			1			2
Ending balance at June 30, 2011	$	25		$	(204	)	$	1		$	295		$	117
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2011	$	-		$	64		$	(1	)	$	(4	)	$	59

	Net derivative commodity contracts
Six Months	Ameren Missouri			Ameren Illinois			Genco			Other(c)			Ameren
Uranium:
Beginning balance at January 1, 2011	$	2		$	(a	)	$	(a	)	$	(a	)	$	2
Realized and unrealized gains (losses):
Included in regulatory assets/liabilities		(4	)		(a	)		(a	)		(a	)		(4	)
Total realized and unrealized gains (losses)		(4	)		(a	)		(a	)		(a	)		(4	)
Ending balance at June 30, 2011	$	(2	)	$	(a	)	$	(a	)	$	(a	)	$	(2	)
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2011	$	(2	)	$	(a	)	$	(a	)	$	(a	)	$	(2	)

(a) Not applicable.

(b) Net gains and losses on fuel oils and natural gas derivative commodity contracts are recorded in Operating Expenses - Fuel, while net gains and losses on power derivative commodity contracts are recorded in Operating Revenues - Electric.

(c) Includes amounts for Merchant Generation nonregistrant subsidiaries and intercompany eliminations, including the elimination of financial power contracts between Ameren Illinois and Marketing Company.

Schedule Of Transfers Between Fair Value Hierarchy Levels

	Three Months					Six Months
	2012			2011		2012			2011
Ameren - derivative commodity contracts:(a)
Transfers into Level 3 / Transfers out of Level 1 - Fuel oils	$	-		$	-	$	2		$	-
Transfers out of Level 3 / Transfers into Level 1 - Fuel oils		-			-		(1	)		-
Transfers out of Level 3 / Transfers into Level 2 - Natural gas		-			-		185			-
Transfers into Level 3 / Transfers out of Level 2 - Power		1			1		1			1
Transfers out of Level 3 / Transfers into Level 2 - Power		-			2		1			2
Net fair value of Level 3 transfers	$	1		$	3	$	188		$	3
Ameren Missouri - derivative commodity contracts:
Transfers into Level 3 / Transfers out of Level 1 - Fuel oils	$	-		$	-	$	2		$	-
Transfers out of Level 3 / Transfers into Level 2 - Natural gas		-			-		15			-
Transfers into Level 3 / Transfers out of Level 2 - Power		-			-		-			(1	)
Transfers out of Level 3 / Transfers into Level 2 - Power		(1	)		1		(2	)		1
Net fair value of Level 3 transfers	$	(1	)	$	1	$	15		$	-
Ameren Illinois - derivative commodity contracts:
Transfers out of Level 3 / Transfers into Level 2 - Natural gas	$	-		$	-	$	170		$	-
Genco - derivative commodity contracts:
Transfers out of Level 3 / Transfers into Level 1 - Fuel oils	$	-		$	-	$	(1	)	$	-

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

Schedule Of Carrying Amounts And Estimated Fair Values Of Long-Term Debt, Capital Lease Obligations And Preferred Stock

	June 30, 2012				December 31, 2011
	Carrying Amount		Fair Value		Carrying Amount		Fair Value
Ameren:(a)(b)
Long-term debt and capital lease obligations (including current portion)	$	6,857	$	7,766	$	6,856	$	7,800
Preferred stock		142		93		142		92
Ameren Missouri:
Long-term debt and capital lease obligations (including current portion)	$	3,950	$	4,619	$	3,950	$	4,541
Preferred stock		80		55		80		55
Ameren Illinois:
Long-term debt (including current portion)	$	1,658	$	1,984	$	1,658	$	1,943
Preferred stock		62		38		62		37
Genco:
Long-term debt (including current portion)	$	824	$	679	$	824	$	839

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

(b) Preferred stock not subject to mandatory redemption of the Ameren subsidiaries along with the 20% noncontrolling interest of EEI is recorded in Noncontrolling Interests on the balance sheet.

Ameren Illinois Company [Member]

Schedule of Valuation Process And Unobservable Inputs

		Fair Value				Valuation Technique(s)	Unobservable Input	Range [Weighted Average]
		Assets Liabilities
Level 3 Derivative asset and liability - commodity contracts(a):
Ameren(b)	Fuel oils	$	6	$	(2)	Discounted Cash Flow	Escalation rate(%)(c)	0.50 - 0.78 [.72]
							Counterparty credit risk(%)(d),(e)	0.12 - 4 [2]
							Ameren credit risk(%)(d),(e)	4 - 23 [9]
						Option model	Volatilities(%)(c)	23 - 33 [26]
	Power(f)		182		(192)	Option model	Volatilities(%)(d)	17 - 143 [34]
							Average bid/ask consensus peak and offpeak pricing - forwards/swaps ($/MWh)(d)	21 - 44 [36]
						Discounted Cash Flow	Average bid/ask consensus peak and offpeak pricing - forwards/swaps ($/MWh)(d)	18 - 51 [34]
							Estimated auction price for FTRs ($/MW)(c)	(672) - 7,200 [138]
							Nodal basis ($/MWh)(c)	(6) - (0.50) [(3)]
							Counterparty credit risk(%)(d),(e)	0.06 - 12 [4]
							Ameren credit risk(%)(d),(e)	4 - 5 [5]
						Fundamental energy production model	Estimated future gas prices ($/mmbtu)(c)	4 - 6 [5]
						Contract price allocation	Estimated renewable energy credit costs ($/credit)(c)	5 - 7 [6]
	Uranium		-		(1)	Discounted Cash Flow	Average bid/ask consensus pricing ($/pound)(c)	62 - 63 [62]
Ameren Missouri	Fuel oils	$	5	$	(2)	Discounted Cash Flow	Escalation rate(%)(c)	0.50 - 0.75 [.65]
							Counterparty credit risk(%)(d),(e)	0.12 - 2 [2]
							Ameren credit risk(%)(d),(e)	5
						Option model	Volatilities(%)(c)	23 - 33 [25]
	Power(f)		31		(5)	Option model	Volatilities(%)(d)	43 - 143 [76]
							Average bid/ask consensus peak and offpeak pricing - ($/MWh)(d)	24 - 32 [27]
						Discounted Cash Flow	Average bid/ask consensus peak and offpeak pricing - forwards/swaps ($/MWh)(d)	21 - 46 [25]
							Estimated auction price for FTRs ($/MW)(c)	(149) - 1,851 [140]
							Nodal basis ($/MWh)(c)	(3) - (0.48) [(2)]
							Counterparty credit risk(%)(d),(e)	0.42 - 12 [7]
							Ameren Missouri credit risk(%)(d),(e)	5
	Uranium		-		(1)	Discounted Cash Flow	Average bid/ask consensus pricing ($/pound)(c)	62 - 63 [62]
Ameren Illinois	Power(f)	$	-	$	(221)	Discounted Cash Flow	Average bid/ask consensus peak and offpeak pricing - forwards/swaps ($/MWh)(c)	19 - 45 [26]
							Nodal basis ($/MWh)(d)	(4) - (1) [(2)]
							Ameren Illinois credit risk (%)(d),(e)	5
						Fundamental energy production model	Estimated future gas prices ($/mmbtu)(c)	4 - 6 [5]
						Contract price allocation	Estimated renewable energy credit costs ($/credit)(c)	5 - 7 [6]
Genco	Fuel oils	$	1	$	-	Discounted Cash Flow	Escalation rate(c)	0.50 - 0.78 [0.71]
							Counterparty credit risk (%)(d),(e)	2
							Genco credit risk(%)(d),(e)	23
						Option model	Volatilities (%)(c)	23 - 33 [24]

(a) The derivative asset and liability balances are presented net of counterparty credit considerations.

(b) Includes amounts for Ameren registrant and nonregistrant subsidiaries and intercompany eliminations.

(c) Generally, significant increases (decreases) in this input in isolation would result in a significantly higher (lower) fair value measurement.

(d) Generally, significant increases (decreases) in this input in isolation would result in a significantly lower (higher) fair value measurement.

(e) Counterparty credit risk is only applied to derivative asset balances. Ameren, Ameren Missouri, Ameren Illinois, and Genco credit risk is only applied to derivative liability balances.

(f) Power valuations utilize visible third party pricing evaluated by month for peak and off-peak through 2015. Valuations beyond 2015 utilize fundamentally modeled pricing by month for peak and off-peak.

Schedule Of Fair Value Hierarchy Of Assets And Liabilities Measured At Fair Value On Recurring Basis

		Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Other Unobservable Inputs (Level 3)		Total
Assets:
Ameren(a)	Derivative assets - commodity contracts(b):
	Fuel oils	$	12	$	-	$	6	$	18
	Natural gas		5		5		-		10
	Power		-		17		182		199
	Total derivative assets - commodity contracts	$	17	$	22	$	188	$	227
	Nuclear Decommissioning Trust Fund(c):
	Cash and cash equivalents	$	4	$	-	$	-	$	4
	Equity securities:
	U.S. large capitalization		247		-		-		247
	Debt securities:
	Corporate bonds		-		43		-		43
	Municipal bonds		-		1		-		1
	U.S. treasury and agency securities		-		87		-		87
	Asset-backed securities		-		12		-		12
	Other		-		1		-		1
	Total Nuclear Decommissioning Trust Fund	$	251	$	144	$	-	$	395
	Total Ameren	$	268	$	166	$	188	$	622
Ameren	Derivative assets - commodity contracts(b):
Missouri	Fuel oils	$	7	$	-	$	5	$	12
	Natural gas		2		-		-		2
	Power		-		10		31		41
	Total derivative assets - commodity contracts	$	9	$	10	$	36	$	55
	Nuclear Decommissioning Trust Fund(c):
	Cash and cash equivalents	$	4	$	-	$	-	$	4
	Equity securities:
	U.S. large capitalization		247		-		-		247
	Debt securities:
	Corporate bonds		-		43		-		43
	Municipal bonds		-		1		-		1
	U.S. treasury and agency securities		-		87		-		87
	Asset-backed securities		-		12		-		12
	Other		-		1		-		1
	Total Nuclear Decommissioning Trust Fund	$	251	$	144	$	-	$	395
	Total Ameren Missouri	$	260	$	154	$	36	$	450
Ameren	Derivative assets - commodity contracts(b):
Illinois	Natural gas	$	-	$	2	$	-	$	2

		Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Other Unobservable Inputs (Level 3)		Total
Genco	Derivative assets - commodity contracts(b):
	Fuel oils	$	4	$	-	$	1	$	5
	Natural gas		2		3		-		5
	Total Genco	$	6	$	3	$	1	$	10
Liabilities:
Ameren(a)	Derivative liabilities - commodity contracts(b):
	Coal	$	10	$	-	$	-	$	10
	Fuel oils		9		-		2		11
	Natural gas		15		153		-		168
	Power		-		22		192		214
	Uranium		-		-		1		1
	Total Ameren	$	34	$	175	$	195	$	404
Ameren	Derivative liabilities - commodity contracts(b):
Missouri	Fuel oils		2		-		2		4
	Natural gas		11		12		-		23
	Power		-		12		5		17
	Uranium		-		-		1		1
	Total Ameren Missouri	$	13	$	24	$	8	$	45
Ameren	Derivative liabilities - commodity contracts(b):
Illinois	Natural gas	$	2	$	142	$	-	$	144
	Power		-		-		221		221
	Total Ameren Illinois	$	2	$	142	$	221	$	365
Genco	Derivative liabilities - commodity contracts(b):
	Coal	$	8	$	-	$	-	$	8
	Fuel oils		5		-		-		5
	Natural gas		1		-		-		1
	Total Genco	$	14	$	-	$	-	$	14

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

(b) The derivative asset and liability balances are presented net of counterparty credit considerations.

(c) Balance excludes $(9) million of receivables, payables, and accrued income, net.

The following table sets forth, by level within the fair value hierarchy, our assets and liabilities measured at fair value on a recurring basis as of December 31, 2011:

		Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Other Unobservable Inputs (Level 3)		Total
Assets:
Ameren(a)	Derivative assets - commodity contracts(b):
	Fuel oils	$	33	$	-	$	4	$	37
	Natural gas		4		-		2		6
	Power		-		2		193		195
	Total derivative assets - commodity contracts	$	37	$	2	$	199	$	238
	Nuclear Decommissioning Trust Fund(c):
	Cash and cash equivalents	$	3	$	-	$	-	$	3
	Equity securities:
	U.S. large capitalization		234		-		-		234
	Debt securities:
	Corporate bonds		-		44		-		44
	Municipal bonds		-		1		-		1
	U.S. treasury and agency securities		-		65		-		65
	Asset-backed securities		-		10		-		10
	Other		-		1		-		1
	Total Nuclear Decommissioning Trust Fund	$	237	$	121	$	-	$	358
	Total Ameren	$	274	$	123	$	199	$	596
Ameren	Derivative assets - commodity contracts(b):
Missouri	Fuel oils	$	20	$	-	$	3	$	23
	Natural gas		2		-		-		2
	Power		-		1		29		30
	Total derivative assets - commodity contracts	$	22	$	1	$	32	$	55

		Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Other Unobservable Inputs (Level 3)		Total
	Nuclear Decommissioning Trust Fund(c):
	Cash and cash equivalents	$	3	$	-	$	-	$	3
	Equity securities:
	U.S. large capitalization		234		-		-		234
	Debt securities:
	Corporate bonds		-		44		-		44
	Municipal bonds		-		1		-		1
	U.S. treasury and agency securities		-		65		-		65
	Asset-backed securities		-		10		-		10
	Other		-		1		-		1
	Total Nuclear Decommissioning Trust Fund	$	237	$	121	$	-	$	358
	Total Ameren Missouri	$	259	$	122	$	32	$	413
Ameren	Derivative assets - commodity contracts(b):
Illinois	Natural gas	$	-	$	-	$	2	$	2
	Power		-		-		77		77
	Total Ameren Illinois	$	-	$	-	$	79	$	79
Genco	Derivative assets - commodity contracts(b):
	Fuel oils	$	10	$	-	$	1	$	11
	Natural gas		2		-		-		2
	Total Genco	$	12	$	-	$	1	$	13
Liabilities:
Ameren(a)	Derivative liabilities - commodity contracts(b):
	Fuel oils	$	2	$	-	$	-	$	2
	Natural gas		22		-		176		198
	Power		-		2		78		80
	Uranium		-		-		1		1
	Total Ameren	$	24	$	2	$	255	$	281
Ameren	Derivative liabilities - commodity contracts(b):
Missouri	Fuel oils	$	1	$	-	$	-	$	1
	Natural gas		12		-		14		26
	Power		-		1		8		9
	Uranium		-		-		1		1
	Total Ameren Missouri	$	13	$	1	$	23	$	37
Ameren	Derivative liabilities - commodity contracts(b):
Illinois	Natural gas		7		-		162		169
	Power		-		-		217		217
	Total Ameren Illinois	$	7	$	-	$	379	$	386
Genco	Derivative liabilities - commodity contracts(b):
	Fuel oils	$	1	$	-	$	-	$	1
	Natural gas		2		-		-		2
	Total Genco	$	3	$	-	$	-	$	3

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

(b) The derivative asset and liability balances are presented net of counterparty credit considerations.

(c) Balance excludes $(1) million of receivables, payables, and accrued income, net.

Schedule Of Changes In The Fair Value Of Financial Assets And Liabilities Classified As Level 3 In The Fair Value Hierarchy

	Net derivative commodity contracts
Three Months	Ameren Missouri			Ameren Illinois			Genco			Other(c)			Ameren
Fuel oils:
Beginning balance at April 1, 2012	$	7		$	(a	)	$	2		$	-		$	9
Realized and unrealized gains (losses):
Included in earnings(b)		-			(a	)		(2	)		-			(2	)
Included in regulatory assets/liabilities		(4	)		(a	)		(a	)		(a	)		(4	)
Total realized and unrealized gains (losses)		(4	)		(a	)		(2	)		-			(6	)
Purchases		2			(a	)		1			-			3
Sales		(1	)		(a	)		-			-			(1	)
Settlements		(1	)		(a	)		-			-			(1	)
Ending balance at June 30, 2012	$	3		$	(a	)	$	1		$	-		$	4
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2012	$	(2	)	$	(a	)	$	-		$	-		$	(2	)

	Net derivative commodity contracts
Three Months	Ameren Missouri			Ameren Illinois			Genco			Other(c)			Ameren
Power:
Beginning balance at April 1, 2012	$	20		$	(284	)	$	-		$	240		$	(24	)
Realized and unrealized gains (losses):
Included in earnings(b)		-			-			-			(1	)		(1	)
Included in OCI		-			-			-			10			10
Included in regulatory assets/liabilities		(4	)		(1	)		(a	)		(5	)		(10	)
Total realized and unrealized gains (losses)		(4	)		(1	)		-			4			(1	)
Purchases		22			-			-			6			28
Sales		-			-			-			6			6
Settlements		(11	)		64			-			(73	)		(20	)
Transfers into Level 3		-			-			-			1			1
Transfers out of Level 3		(1	)		-			-			1			-
Ending balance at June 30, 2012	$	26		$	(221	)	$	-		$	185		$	(10	)
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2012	$	(1	)	$	(6	)	$	-		$	8		$	1
Uranium:
Beginning balance at April 1, 2012	$	(1	)	$	(a	)	$	(a	)	$	(a	)	$	(1	)
Realized and unrealized gains (losses):
Included in regulatory assets/liabilities		-			(a	)		(a	)		(a	)		-
Total realized and unrealized gains (losses)		-			(a	)		(a	)		(a	)		-
Ending balance at June 30, 2012	$	(1	)	$	(a	)	$	(a	)	$	(a	)	$	(1	)
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2012	$	-		$	(a	)	$	(a	)	$	(a	)	$	-

(a) Not applicable.

(b) Net gains and losses on fuel oils and natural gas derivative commodity contracts are recorded in “Operating Expenses - Fuel”, while net gains and losses on power derivative commodity contracts are recorded in “Operating Revenues - Electric”.

(c) Includes amounts for Merchant Generation nonregistrant subsidiaries and intercompany eliminations, including the elimination of financial power contracts between Ameren Illinois and Marketing Company.

The following table summarizes the changes in the fair value of financial assets and liabilities classified as Level 3 in the fair value hierarchy for the three months ended June 30, 2011:

	Net derivative commodity contracts
Three Months	Ameren Missouri			Ameren Illinois			Genco			Other(c)			Ameren
Fuel oils:
Beginning balance at April 1, 2011	$	57		$	(a	)	$	29		$	10		$	96
Realized and unrealized gains (losses):
Included in earnings(b)		-			(a	)		(3	)		(2	)		(5	)
Included in regulatory assets/liabilities		(9	)		(a	)		(a	)		(a	)		(9	)
Total realized and unrealized gains (losses)		(9	)		(a	)		(3	)		(2	)		(14	)
Purchases		1			(a	)		-			-			1
Settlements		(8	)		(a	)		(5	)		(2	)		(15	)
Ending balance at June 30, 2011	$	41		$	(a	)	$	21		$	6		$	68
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2011	$	(8	)	$	(a	)	$	(4	)	$	(2	)	$	(14	)
Natural gas:
Beginning balance at April 1, 2011	$	(12	)	$	(108	)	$	-		$	-		$	(120	)
Realized and unrealized gains (losses):
Included in regulatory assets/liabilities		(1	)		(19	)		(a	)		(a	)		(20	)
Total realized and unrealized gains (losses)		(1	)		(19	)		-			-			(20	)
Purchases		-			1			-			-			1
Settlements		2			20			-			-			22
Ending balance at June 30, 2011	$	(11	)	$	(106	)	$	-		$	-		$	(117	)
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2011	$	(1	)	$	(17	)	$	-		$	-		$	(18	)
Power:
Beginning balance at April 1, 2011	$	2		$	(325	)	$	3		$	351		$	31
Realized and unrealized gains (losses):
Included in earnings(b)		-			-			(1	)		(14	)		(15	)
Included in OCI		-			-			-			5			5
Included in regulatory assets/liabilities		(1	)		77			(a	)		(10	)		66
Total realized and unrealized gains (losses)		(1	)		77			(1	)		(19	)		56

	Net derivative commodity contracts
Three Months	Ameren Missouri			Ameren Illinois			Genco			Other(c)			Ameren
Purchases	$	29		$	-		$	-		$	21		$	50
Sales		-			-			-			(7	)		(7	)
Settlements		(6	)		44			(1	)		(53	)		(16	)
Transfers into Level 3		-			-			-			1			1
Transfers out of Level 3		1			-			-			1			2
Ending balance at June 30, 2011	$	25		$	(204	)	$	1		$	295		$	117
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2011	$	(1	)	$	68		$	(1	)	$	(7	)	$	59
Uranium:
Beginning balance at April 1, 2011	$	1		$	(a	)	$	(a	)	$	(a	)	$	1
Realized and unrealized gains (losses):
Included in regulatory assets/liabilities		(3	)		(a	)		(a	)		(a	)		(3	)
Total realized and unrealized gains (losses)		(3	)		(a	)		(a	)		(a	)		(3	)
Ending balance at June 30, 2011	$	(2	)	$	(a	)	$	(a	)	$	(a	)	$	(2	)
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2011	$	(2	)	$	(a	)	$	(a	)	$	(a	)	$	(2	)

(a) Not applicable.

(b) Net gains and losses on fuel oils and natural gas derivative commodity contracts are recorded in Operating Expenses - Fuel, while net gains and losses on power derivative commodity contracts are recorded in Operating Revenues - Electric.

(c) Includes amounts for Merchant Generation nonregistrant subsidiaries and intercompany eliminations, including the elimination of financial power contracts between Ameren Illinois and Marketing Company.

The following table summarizes the changes in the fair value of financial assets and liabilities classified as Level 3 in the fair value hierarchy for the six months ended June 30, 2012:

	Net derivative commodity contracts
Six Months	Ameren Missouri			Ameren Illinois			Genco			Other(c)			Ameren
Fuel oils:
Beginning balance at January 1, 2012	$	3		$	(a	)	$	1		$	-		$	4
Realized and unrealized gains (losses):
Included in earnings(b)		-			(a	)		-			-			-
Included in regulatory assets/liabilities		(2	)		(a	)		(a	)		(a	)		(2	)
Total realized and unrealized gains (losses)		(2	)		(a	)		-			-			(2	)
Purchases		2			(a	)		1			-			3
Sales		(1	)		(a	)		-			-			(1	)
Settlements		(1	)		(a	)		-			-			(1	)
Transfers into Level 3		2			(a	)		-			-			2
Transfers out of Level 3		-			(a	)		(1	)		-			(1	)
Ending balance at June 30, 2012	$	3		$	(a	)	$	1		$	-		$	4
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2012	$	(1	)	$	(a	)	$	-		$	-		$	(1	)
Natural gas:
Beginning balance at January 1, 2012	$	(14	)	$	(160	)	$	-		$	-		$	(174	)
Realized and unrealized gains (losses):
Included in regulatory assets/liabilities		(2	)		(26	)		(a	)		(a	)		(28	)
Total realized and unrealized gains (losses)		(2	)		(26	)		-			-			(28	)
Settlements		1			16			-			-			17
Transfer out of Level 3		15			170			-			-			185
Ending balance at June 30, 2012	$	-		$	-		$	-		$	-		$	-
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2012	$	9		$	114		$	-		$	-		$	123
Power:
Beginning balance at January 1, 2012	$	21		$	(140	)	$	-		$	234		$	115
Realized and unrealized gains (losses):
Included in earnings(b)		-			-			-			7			7
Included in OCI		-			-			-			34			34
Included in regulatory assets/liabilities		9			(221	)		(a	)		44			(168	)
Total realized and unrealized gains (losses)		9			(221	)		-			85			(127	)
Purchases		22			-			-			5			27
Sales		-			-			-			7			7
Settlements		(24	)		140			-			(150	)		(34	)
Transfers into Level 3		-			-			-			1			1

	Net derivative commodity contracts
Six Months	Ameren Missouri			Ameren Illinois			Genco			Other(c)			Ameren
Transfers out of Level 3		(2	)		-			-			3			1
Ending balance at June 30, 2012	$	26		$	(221	)	$	-		$	185		$	(10	)
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2012	$	3		$	(195	)(d)	$	-		$	42		$	(150	)
Uranium:
Beginning balance at January 1, 2012	$	(1	)	$	(a	)	$	(a	)	$	(a	)	$	(1	)
Realized and unrealized gains (losses):
Included in regulatory assets/liabilities		-			(a	)		(a	)		(a	)		-
Total realized and unrealized gains (losses)		-			(a	)		(a	)		(a	)		-
Ending balance at June 30, 2012	$	(1	)	$	(a	)	$	(a	)	$	(a	)	$	(1	)
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2012	$	-		$	(a	)	$	(a	)	$	(a	)	$	-

(a) Not applicable.

(b) Net gains and losses on fuel oils and natural gas derivative commodity contracts are recorded in “Operating Expenses - Fuel”, while net gains and losses on power derivative commodity contracts are recorded in “Operating Revenues - Electric”.

(c) Includes amounts for Merchant Generation nonregistrant subsidiaries and intercompany eliminations, including the elimination of financial power contracts between Ameren Illinois and Marketing Company.

(d) The change in unrealized losses was due to decreases in long-term power prices applied to 20-year Ameren Illinois’ swap contracts, which expire in May 2032.

The following table summarizes the changes in the fair value of financial assets and liabilities classified as Level 3 in the fair value hierarchy for the six months ended June 30, 2011:

	Net derivative commodity contracts
Six Months	Ameren Missouri			Ameren Illinois			Genco			Other(c)			Ameren
Fuel oils:
Beginning balance at January 1, 2011	$	30		$	(a	)	$	17		$	4		$	51
Realized and unrealized gains (losses):
Included in earnings(b)		-			(a	)		12			5			17
Included in regulatory assets/liabilities		22			(a	)		(a	)		(a	)		22
Total realized and unrealized gains (losses)		22			(a	)		12			5			39
Purchases		2			(a	)		-			-			2
Settlements		(13	)		(a	)		(8	)		(3	)		(24	)
Ending balance at June 30, 2011	$	41		$	(a	)	$	21		$	6		$	68
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2011	$	18		$	(a	)	$	9		$	3		$	30
Natural gas:
Beginning balance at January 1, 2011	$	(14	)	$	(134	)	$	-		$	-		$	(148	)
Realized and unrealized gains (losses):
Included in regulatory assets/liabilities		(1	)		(12	)		(a	)		(a	)		(13	)
Total realized and unrealized gains (losses)		(1	)		(12	)		-			-			(13	)
Purchases		-			1			-			-			1
Settlements		4			39			-			-			43
Ending balance at June 30, 2011	$	(11	)	$	(106	)	$	-		$	-		$	(117	)
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2011	$	1		$	8		$	-		$	-		$	9
Power:
Beginning balance at January 1, 2011	$	2		$	(352	)	$	3		$	383		$	36
Realized and unrealized gains (losses):
Included in earnings(b)		-			-			(1	)		(17	)		(18	)
Included in OCI		-			-			-			5			5
Included in regulatory assets/liabilities		6			47			(a	)		11			64
Total realized and unrealized gains (losses)		6			47			(1	)		(1	)		51
Purchases		29			-			-			30			59
Sales		-			-			-			(16	)		(16	)
Settlements		(12	)		101			(1	)		(104	)		(16	)
Transfers into Level 3		(1	)		-			-			2			1
Transfers out of Level 3		1			-			-			1			2
Ending balance at June 30, 2011	$	25		$	(204	)	$	1		$	295		$	117
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2011	$	-		$	64		$	(1	)	$	(4	)	$	59

	Net derivative commodity contracts
Six Months	Ameren Missouri			Ameren Illinois			Genco			Other(c)			Ameren
Uranium:
Beginning balance at January 1, 2011	$	2		$	(a	)	$	(a	)	$	(a	)	$	2
Realized and unrealized gains (losses):
Included in regulatory assets/liabilities		(4	)		(a	)		(a	)		(a	)		(4	)
Total realized and unrealized gains (losses)		(4	)		(a	)		(a	)		(a	)		(4	)
Ending balance at June 30, 2011	$	(2	)	$	(a	)	$	(a	)	$	(a	)	$	(2	)
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2011	$	(2	)	$	(a	)	$	(a	)	$	(a	)	$	(2	)

(a) Not applicable.

(b) Net gains and losses on fuel oils and natural gas derivative commodity contracts are recorded in Operating Expenses - Fuel, while net gains and losses on power derivative commodity contracts are recorded in Operating Revenues - Electric.

(c) Includes amounts for Merchant Generation nonregistrant subsidiaries and intercompany eliminations, including the elimination of financial power contracts between Ameren Illinois and Marketing Company.

Schedule Of Transfers Between Fair Value Hierarchy Levels

	Three Months					Six Months
	2012			2011		2012			2011
Ameren - derivative commodity contracts:(a)
Transfers into Level 3 / Transfers out of Level 1 - Fuel oils	$	-		$	-	$	2		$	-
Transfers out of Level 3 / Transfers into Level 1 - Fuel oils		-			-		(1	)		-
Transfers out of Level 3 / Transfers into Level 2 - Natural gas		-			-		185			-
Transfers into Level 3 / Transfers out of Level 2 - Power		1			1		1			1
Transfers out of Level 3 / Transfers into Level 2 - Power		-			2		1			2
Net fair value of Level 3 transfers	$	1		$	3	$	188		$	3
Ameren Missouri - derivative commodity contracts:
Transfers into Level 3 / Transfers out of Level 1 - Fuel oils	$	-		$	-	$	2		$	-
Transfers out of Level 3 / Transfers into Level 2 - Natural gas		-			-		15			-
Transfers into Level 3 / Transfers out of Level 2 - Power		-			-		-			(1	)
Transfers out of Level 3 / Transfers into Level 2 - Power		(1	)		1		(2	)		1
Net fair value of Level 3 transfers	$	(1	)	$	1	$	15		$	-
Ameren Illinois - derivative commodity contracts:
Transfers out of Level 3 / Transfers into Level 2 - Natural gas	$	-		$	-	$	170		$	-
Genco - derivative commodity contracts:
Transfers out of Level 3 / Transfers into Level 1 - Fuel oils	$	-		$	-	$	(1	)	$	-

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

Schedule Of Carrying Amounts And Estimated Fair Values Of Long-Term Debt, Capital Lease Obligations And Preferred Stock

	June 30, 2012				December 31, 2011
	Carrying Amount		Fair Value		Carrying Amount		Fair Value
Ameren:(a)(b)
Long-term debt and capital lease obligations (including current portion)	$	6,857	$	7,766	$	6,856	$	7,800
Preferred stock		142		93		142		92
Ameren Missouri:
Long-term debt and capital lease obligations (including current portion)	$	3,950	$	4,619	$	3,950	$	4,541
Preferred stock		80		55		80		55
Ameren Illinois:
Long-term debt (including current portion)	$	1,658	$	1,984	$	1,658	$	1,943
Preferred stock		62		38		62		37
Genco:
Long-term debt (including current portion)	$	824	$	679	$	824	$	839

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

(b) Preferred stock not subject to mandatory redemption of the Ameren subsidiaries along with the 20% noncontrolling interest of EEI is recorded in Noncontrolling Interests on the balance sheet.

Ameren Energy Generating Company [Member]

Schedule of Valuation Process And Unobservable Inputs

		Fair Value				Valuation Technique(s)	Unobservable Input	Range [Weighted Average]
		Assets Liabilities
Level 3 Derivative asset and liability - commodity contracts(a):
Ameren(b)	Fuel oils	$	6	$	(2)	Discounted Cash Flow	Escalation rate(%)(c)	0.50 - 0.78 [.72]
							Counterparty credit risk(%)(d),(e)	0.12 - 4 [2]
							Ameren credit risk(%)(d),(e)	4 - 23 [9]
						Option model	Volatilities(%)(c)	23 - 33 [26]
	Power(f)		182		(192)	Option model	Volatilities(%)(d)	17 - 143 [34]
							Average bid/ask consensus peak and offpeak pricing - forwards/swaps ($/MWh)(d)	21 - 44 [36]
						Discounted Cash Flow	Average bid/ask consensus peak and offpeak pricing - forwards/swaps ($/MWh)(d)	18 - 51 [34]
							Estimated auction price for FTRs ($/MW)(c)	(672) - 7,200 [138]
							Nodal basis ($/MWh)(c)	(6) - (0.50) [(3)]
							Counterparty credit risk(%)(d),(e)	0.06 - 12 [4]
							Ameren credit risk(%)(d),(e)	4 - 5 [5]
						Fundamental energy production model	Estimated future gas prices ($/mmbtu)(c)	4 - 6 [5]
						Contract price allocation	Estimated renewable energy credit costs ($/credit)(c)	5 - 7 [6]
	Uranium		-		(1)	Discounted Cash Flow	Average bid/ask consensus pricing ($/pound)(c)	62 - 63 [62]
Ameren Missouri	Fuel oils	$	5	$	(2)	Discounted Cash Flow	Escalation rate(%)(c)	0.50 - 0.75 [.65]
							Counterparty credit risk(%)(d),(e)	0.12 - 2 [2]
							Ameren credit risk(%)(d),(e)	5
						Option model	Volatilities(%)(c)	23 - 33 [25]
	Power(f)		31		(5)	Option model	Volatilities(%)(d)	43 - 143 [76]
							Average bid/ask consensus peak and offpeak pricing - ($/MWh)(d)	24 - 32 [27]
						Discounted Cash Flow	Average bid/ask consensus peak and offpeak pricing - forwards/swaps ($/MWh)(d)	21 - 46 [25]
							Estimated auction price for FTRs ($/MW)(c)	(149) - 1,851 [140]
							Nodal basis ($/MWh)(c)	(3) - (0.48) [(2)]
							Counterparty credit risk(%)(d),(e)	0.42 - 12 [7]
							Ameren Missouri credit risk(%)(d),(e)	5
	Uranium		-		(1)	Discounted Cash Flow	Average bid/ask consensus pricing ($/pound)(c)	62 - 63 [62]
Ameren Illinois	Power(f)	$	-	$	(221)	Discounted Cash Flow	Average bid/ask consensus peak and offpeak pricing - forwards/swaps ($/MWh)(c)	19 - 45 [26]
							Nodal basis ($/MWh)(d)	(4) - (1) [(2)]
							Ameren Illinois credit risk (%)(d),(e)	5
						Fundamental energy production model	Estimated future gas prices ($/mmbtu)(c)	4 - 6 [5]
						Contract price allocation	Estimated renewable energy credit costs ($/credit)(c)	5 - 7 [6]
Genco	Fuel oils	$	1	$	-	Discounted Cash Flow	Escalation rate(c)	0.50 - 0.78 [0.71]
							Counterparty credit risk (%)(d),(e)	2
							Genco credit risk(%)(d),(e)	23
						Option model	Volatilities (%)(c)	23 - 33 [24]

(a) The derivative asset and liability balances are presented net of counterparty credit considerations.

(b) Includes amounts for Ameren registrant and nonregistrant subsidiaries and intercompany eliminations.

(c) Generally, significant increases (decreases) in this input in isolation would result in a significantly higher (lower) fair value measurement.

(d) Generally, significant increases (decreases) in this input in isolation would result in a significantly lower (higher) fair value measurement.

(e) Counterparty credit risk is only applied to derivative asset balances. Ameren, Ameren Missouri, Ameren Illinois, and Genco credit risk is only applied to derivative liability balances.

(f) Power valuations utilize visible third party pricing evaluated by month for peak and off-peak through 2015. Valuations beyond 2015 utilize fundamentally modeled pricing by month for peak and off-peak.

Schedule Of Fair Value Hierarchy Of Assets And Liabilities Measured At Fair Value On Recurring Basis

		Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Other Unobservable Inputs (Level 3)		Total
Assets:
Ameren(a)	Derivative assets - commodity contracts(b):
	Fuel oils	$	12	$	-	$	6	$	18
	Natural gas		5		5		-		10
	Power		-		17		182		199
	Total derivative assets - commodity contracts	$	17	$	22	$	188	$	227
	Nuclear Decommissioning Trust Fund(c):
	Cash and cash equivalents	$	4	$	-	$	-	$	4
	Equity securities:
	U.S. large capitalization		247		-		-		247
	Debt securities:
	Corporate bonds		-		43		-		43
	Municipal bonds		-		1		-		1
	U.S. treasury and agency securities		-		87		-		87
	Asset-backed securities		-		12		-		12
	Other		-		1		-		1
	Total Nuclear Decommissioning Trust Fund	$	251	$	144	$	-	$	395
	Total Ameren	$	268	$	166	$	188	$	622
Ameren	Derivative assets - commodity contracts(b):
Missouri	Fuel oils	$	7	$	-	$	5	$	12
	Natural gas		2		-		-		2
	Power		-		10		31		41
	Total derivative assets - commodity contracts	$	9	$	10	$	36	$	55
	Nuclear Decommissioning Trust Fund(c):
	Cash and cash equivalents	$	4	$	-	$	-	$	4
	Equity securities:
	U.S. large capitalization		247		-		-		247
	Debt securities:
	Corporate bonds		-		43		-		43
	Municipal bonds		-		1		-		1
	U.S. treasury and agency securities		-		87		-		87
	Asset-backed securities		-		12		-		12
	Other		-		1		-		1
	Total Nuclear Decommissioning Trust Fund	$	251	$	144	$	-	$	395
	Total Ameren Missouri	$	260	$	154	$	36	$	450
Ameren	Derivative assets - commodity contracts(b):
Illinois	Natural gas	$	-	$	2	$	-	$	2

		Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Other Unobservable Inputs (Level 3)		Total
Genco	Derivative assets - commodity contracts(b):
	Fuel oils	$	4	$	-	$	1	$	5
	Natural gas		2		3		-		5
	Total Genco	$	6	$	3	$	1	$	10
Liabilities:
Ameren(a)	Derivative liabilities - commodity contracts(b):
	Coal	$	10	$	-	$	-	$	10
	Fuel oils		9		-		2		11
	Natural gas		15		153		-		168
	Power		-		22		192		214
	Uranium		-		-		1		1
	Total Ameren	$	34	$	175	$	195	$	404
Ameren	Derivative liabilities - commodity contracts(b):
Missouri	Fuel oils		2		-		2		4
	Natural gas		11		12		-		23
	Power		-		12		5		17
	Uranium		-		-		1		1
	Total Ameren Missouri	$	13	$	24	$	8	$	45
Ameren	Derivative liabilities - commodity contracts(b):
Illinois	Natural gas	$	2	$	142	$	-	$	144
	Power		-		-		221		221
	Total Ameren Illinois	$	2	$	142	$	221	$	365
Genco	Derivative liabilities - commodity contracts(b):
	Coal	$	8	$	-	$	-	$	8
	Fuel oils		5		-		-		5
	Natural gas		1		-		-		1
	Total Genco	$	14	$	-	$	-	$	14

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

(b) The derivative asset and liability balances are presented net of counterparty credit considerations.

(c) Balance excludes $(9) million of receivables, payables, and accrued income, net.

The following table sets forth, by level within the fair value hierarchy, our assets and liabilities measured at fair value on a recurring basis as of December 31, 2011:

		Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Other Unobservable Inputs (Level 3)		Total
Assets:
Ameren(a)	Derivative assets - commodity contracts(b):
	Fuel oils	$	33	$	-	$	4	$	37
	Natural gas		4		-		2		6
	Power		-		2		193		195
	Total derivative assets - commodity contracts	$	37	$	2	$	199	$	238
	Nuclear Decommissioning Trust Fund(c):
	Cash and cash equivalents	$	3	$	-	$	-	$	3
	Equity securities:
	U.S. large capitalization		234		-		-		234
	Debt securities:
	Corporate bonds		-		44		-		44
	Municipal bonds		-		1		-		1
	U.S. treasury and agency securities		-		65		-		65
	Asset-backed securities		-		10		-		10
	Other		-		1		-		1
	Total Nuclear Decommissioning Trust Fund	$	237	$	121	$	-	$	358
	Total Ameren	$	274	$	123	$	199	$	596
Ameren	Derivative assets - commodity contracts(b):
Missouri	Fuel oils	$	20	$	-	$	3	$	23
	Natural gas		2		-		-		2
	Power		-		1		29		30
	Total derivative assets - commodity contracts	$	22	$	1	$	32	$	55

		Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Other Unobservable Inputs (Level 3)		Total
	Nuclear Decommissioning Trust Fund(c):
	Cash and cash equivalents	$	3	$	-	$	-	$	3
	Equity securities:
	U.S. large capitalization		234		-		-		234
	Debt securities:
	Corporate bonds		-		44		-		44
	Municipal bonds		-		1		-		1
	U.S. treasury and agency securities		-		65		-		65
	Asset-backed securities		-		10		-		10
	Other		-		1		-		1
	Total Nuclear Decommissioning Trust Fund	$	237	$	121	$	-	$	358
	Total Ameren Missouri	$	259	$	122	$	32	$	413
Ameren	Derivative assets - commodity contracts(b):
Illinois	Natural gas	$	-	$	-	$	2	$	2
	Power		-		-		77		77
	Total Ameren Illinois	$	-	$	-	$	79	$	79
Genco	Derivative assets - commodity contracts(b):
	Fuel oils	$	10	$	-	$	1	$	11
	Natural gas		2		-		-		2
	Total Genco	$	12	$	-	$	1	$	13
Liabilities:
Ameren(a)	Derivative liabilities - commodity contracts(b):
	Fuel oils	$	2	$	-	$	-	$	2
	Natural gas		22		-		176		198
	Power		-		2		78		80
	Uranium		-		-		1		1
	Total Ameren	$	24	$	2	$	255	$	281
Ameren	Derivative liabilities - commodity contracts(b):
Missouri	Fuel oils	$	1	$	-	$	-	$	1
	Natural gas		12		-		14		26
	Power		-		1		8		9
	Uranium		-		-		1		1
	Total Ameren Missouri	$	13	$	1	$	23	$	37
Ameren	Derivative liabilities - commodity contracts(b):
Illinois	Natural gas		7		-		162		169
	Power		-		-		217		217
	Total Ameren Illinois	$	7	$	-	$	379	$	386
Genco	Derivative liabilities - commodity contracts(b):
	Fuel oils	$	1	$	-	$	-	$	1
	Natural gas		2		-		-		2
	Total Genco	$	3	$	-	$	-	$	3

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

(b) The derivative asset and liability balances are presented net of counterparty credit considerations.

(c) Balance excludes $(1) million of receivables, payables, and accrued income, net.

Schedule Of Changes In The Fair Value Of Financial Assets And Liabilities Classified As Level 3 In The Fair Value Hierarchy

	Net derivative commodity contracts
Three Months	Ameren Missouri			Ameren Illinois			Genco			Other(c)			Ameren
Fuel oils:
Beginning balance at April 1, 2012	$	7		$	(a	)	$	2		$	-		$	9
Realized and unrealized gains (losses):
Included in earnings(b)		-			(a	)		(2	)		-			(2	)
Included in regulatory assets/liabilities		(4	)		(a	)		(a	)		(a	)		(4	)
Total realized and unrealized gains (losses)		(4	)		(a	)		(2	)		-			(6	)
Purchases		2			(a	)		1			-			3
Sales		(1	)		(a	)		-			-			(1	)
Settlements		(1	)		(a	)		-			-			(1	)
Ending balance at June 30, 2012	$	3		$	(a	)	$	1		$	-		$	4
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2012	$	(2	)	$	(a	)	$	-		$	-		$	(2	)

	Net derivative commodity contracts
Three Months	Ameren Missouri			Ameren Illinois			Genco			Other(c)			Ameren
Power:
Beginning balance at April 1, 2012	$	20		$	(284	)	$	-		$	240		$	(24	)
Realized and unrealized gains (losses):
Included in earnings(b)		-			-			-			(1	)		(1	)
Included in OCI		-			-			-			10			10
Included in regulatory assets/liabilities		(4	)		(1	)		(a	)		(5	)		(10	)
Total realized and unrealized gains (losses)		(4	)		(1	)		-			4			(1	)
Purchases		22			-			-			6			28
Sales		-			-			-			6			6
Settlements		(11	)		64			-			(73	)		(20	)
Transfers into Level 3		-			-			-			1			1
Transfers out of Level 3		(1	)		-			-			1			-
Ending balance at June 30, 2012	$	26		$	(221	)	$	-		$	185		$	(10	)
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2012	$	(1	)	$	(6	)	$	-		$	8		$	1
Uranium:
Beginning balance at April 1, 2012	$	(1	)	$	(a	)	$	(a	)	$	(a	)	$	(1	)
Realized and unrealized gains (losses):
Included in regulatory assets/liabilities		-			(a	)		(a	)		(a	)		-
Total realized and unrealized gains (losses)		-			(a	)		(a	)		(a	)		-
Ending balance at June 30, 2012	$	(1	)	$	(a	)	$	(a	)	$	(a	)	$	(1	)
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2012	$	-		$	(a	)	$	(a	)	$	(a	)	$	-

(a) Not applicable.

(b) Net gains and losses on fuel oils and natural gas derivative commodity contracts are recorded in “Operating Expenses - Fuel”, while net gains and losses on power derivative commodity contracts are recorded in “Operating Revenues - Electric”.

(c) Includes amounts for Merchant Generation nonregistrant subsidiaries and intercompany eliminations, including the elimination of financial power contracts between Ameren Illinois and Marketing Company.

The following table summarizes the changes in the fair value of financial assets and liabilities classified as Level 3 in the fair value hierarchy for the three months ended June 30, 2011:

	Net derivative commodity contracts
Three Months	Ameren Missouri			Ameren Illinois			Genco			Other(c)			Ameren
Fuel oils:
Beginning balance at April 1, 2011	$	57		$	(a	)	$	29		$	10		$	96
Realized and unrealized gains (losses):
Included in earnings(b)		-			(a	)		(3	)		(2	)		(5	)
Included in regulatory assets/liabilities		(9	)		(a	)		(a	)		(a	)		(9	)
Total realized and unrealized gains (losses)		(9	)		(a	)		(3	)		(2	)		(14	)
Purchases		1			(a	)		-			-			1
Settlements		(8	)		(a	)		(5	)		(2	)		(15	)
Ending balance at June 30, 2011	$	41		$	(a	)	$	21		$	6		$	68
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2011	$	(8	)	$	(a	)	$	(4	)	$	(2	)	$	(14	)
Natural gas:
Beginning balance at April 1, 2011	$	(12	)	$	(108	)	$	-		$	-		$	(120	)
Realized and unrealized gains (losses):
Included in regulatory assets/liabilities		(1	)		(19	)		(a	)		(a	)		(20	)
Total realized and unrealized gains (losses)		(1	)		(19	)		-			-			(20	)
Purchases		-			1			-			-			1
Settlements		2			20			-			-			22
Ending balance at June 30, 2011	$	(11	)	$	(106	)	$	-		$	-		$	(117	)
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2011	$	(1	)	$	(17	)	$	-		$	-		$	(18	)
Power:
Beginning balance at April 1, 2011	$	2		$	(325	)	$	3		$	351		$	31
Realized and unrealized gains (losses):
Included in earnings(b)		-			-			(1	)		(14	)		(15	)
Included in OCI		-			-			-			5			5
Included in regulatory assets/liabilities		(1	)		77			(a	)		(10	)		66
Total realized and unrealized gains (losses)		(1	)		77			(1	)		(19	)		56

	Net derivative commodity contracts
Three Months	Ameren Missouri			Ameren Illinois			Genco			Other(c)			Ameren
Purchases	$	29		$	-		$	-		$	21		$	50
Sales		-			-			-			(7	)		(7	)
Settlements		(6	)		44			(1	)		(53	)		(16	)
Transfers into Level 3		-			-			-			1			1
Transfers out of Level 3		1			-			-			1			2
Ending balance at June 30, 2011	$	25		$	(204	)	$	1		$	295		$	117
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2011	$	(1	)	$	68		$	(1	)	$	(7	)	$	59
Uranium:
Beginning balance at April 1, 2011	$	1		$	(a	)	$	(a	)	$	(a	)	$	1
Realized and unrealized gains (losses):
Included in regulatory assets/liabilities		(3	)		(a	)		(a	)		(a	)		(3	)
Total realized and unrealized gains (losses)		(3	)		(a	)		(a	)		(a	)		(3	)
Ending balance at June 30, 2011	$	(2	)	$	(a	)	$	(a	)	$	(a	)	$	(2	)
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2011	$	(2	)	$	(a	)	$	(a	)	$	(a	)	$	(2	)

(a) Not applicable.

(b) Net gains and losses on fuel oils and natural gas derivative commodity contracts are recorded in Operating Expenses - Fuel, while net gains and losses on power derivative commodity contracts are recorded in Operating Revenues - Electric.

(c) Includes amounts for Merchant Generation nonregistrant subsidiaries and intercompany eliminations, including the elimination of financial power contracts between Ameren Illinois and Marketing Company.

The following table summarizes the changes in the fair value of financial assets and liabilities classified as Level 3 in the fair value hierarchy for the six months ended June 30, 2012:

	Net derivative commodity contracts
Six Months	Ameren Missouri			Ameren Illinois			Genco			Other(c)			Ameren
Fuel oils:
Beginning balance at January 1, 2012	$	3		$	(a	)	$	1		$	-		$	4
Realized and unrealized gains (losses):
Included in earnings(b)		-			(a	)		-			-			-
Included in regulatory assets/liabilities		(2	)		(a	)		(a	)		(a	)		(2	)
Total realized and unrealized gains (losses)		(2	)		(a	)		-			-			(2	)
Purchases		2			(a	)		1			-			3
Sales		(1	)		(a	)		-			-			(1	)
Settlements		(1	)		(a	)		-			-			(1	)
Transfers into Level 3		2			(a	)		-			-			2
Transfers out of Level 3		-			(a	)		(1	)		-			(1	)
Ending balance at June 30, 2012	$	3		$	(a	)	$	1		$	-		$	4
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2012	$	(1	)	$	(a	)	$	-		$	-		$	(1	)
Natural gas:
Beginning balance at January 1, 2012	$	(14	)	$	(160	)	$	-		$	-		$	(174	)
Realized and unrealized gains (losses):
Included in regulatory assets/liabilities		(2	)		(26	)		(a	)		(a	)		(28	)
Total realized and unrealized gains (losses)		(2	)		(26	)		-			-			(28	)
Settlements		1			16			-			-			17
Transfer out of Level 3		15			170			-			-			185
Ending balance at June 30, 2012	$	-		$	-		$	-		$	-		$	-
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2012	$	9		$	114		$	-		$	-		$	123
Power:
Beginning balance at January 1, 2012	$	21		$	(140	)	$	-		$	234		$	115
Realized and unrealized gains (losses):
Included in earnings(b)		-			-			-			7			7
Included in OCI		-			-			-			34			34
Included in regulatory assets/liabilities		9			(221	)		(a	)		44			(168	)
Total realized and unrealized gains (losses)		9			(221	)		-			85			(127	)
Purchases		22			-			-			5			27
Sales		-			-			-			7			7
Settlements		(24	)		140			-			(150	)		(34	)
Transfers into Level 3		-			-			-			1			1

	Net derivative commodity contracts
Six Months	Ameren Missouri			Ameren Illinois			Genco			Other(c)			Ameren
Transfers out of Level 3		(2	)		-			-			3			1
Ending balance at June 30, 2012	$	26		$	(221	)	$	-		$	185		$	(10	)
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2012	$	3		$	(195	)(d)	$	-		$	42		$	(150	)
Uranium:
Beginning balance at January 1, 2012	$	(1	)	$	(a	)	$	(a	)	$	(a	)	$	(1	)
Realized and unrealized gains (losses):
Included in regulatory assets/liabilities		-			(a	)		(a	)		(a	)		-
Total realized and unrealized gains (losses)		-			(a	)		(a	)		(a	)		-
Ending balance at June 30, 2012	$	(1	)	$	(a	)	$	(a	)	$	(a	)	$	(1	)
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2012	$	-		$	(a	)	$	(a	)	$	(a	)	$	-

(a) Not applicable.

(b) Net gains and losses on fuel oils and natural gas derivative commodity contracts are recorded in “Operating Expenses - Fuel”, while net gains and losses on power derivative commodity contracts are recorded in “Operating Revenues - Electric”.

(c) Includes amounts for Merchant Generation nonregistrant subsidiaries and intercompany eliminations, including the elimination of financial power contracts between Ameren Illinois and Marketing Company.

(d) The change in unrealized losses was due to decreases in long-term power prices applied to 20-year Ameren Illinois’ swap contracts, which expire in May 2032.

The following table summarizes the changes in the fair value of financial assets and liabilities classified as Level 3 in the fair value hierarchy for the six months ended June 30, 2011:

	Net derivative commodity contracts
Six Months	Ameren Missouri			Ameren Illinois			Genco			Other(c)			Ameren
Fuel oils:
Beginning balance at January 1, 2011	$	30		$	(a	)	$	17		$	4		$	51
Realized and unrealized gains (losses):
Included in earnings(b)		-			(a	)		12			5			17
Included in regulatory assets/liabilities		22			(a	)		(a	)		(a	)		22
Total realized and unrealized gains (losses)		22			(a	)		12			5			39
Purchases		2			(a	)		-			-			2
Settlements		(13	)		(a	)		(8	)		(3	)		(24	)
Ending balance at June 30, 2011	$	41		$	(a	)	$	21		$	6		$	68
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2011	$	18		$	(a	)	$	9		$	3		$	30
Natural gas:
Beginning balance at January 1, 2011	$	(14	)	$	(134	)	$	-		$	-		$	(148	)
Realized and unrealized gains (losses):
Included in regulatory assets/liabilities		(1	)		(12	)		(a	)		(a	)		(13	)
Total realized and unrealized gains (losses)		(1	)		(12	)		-			-			(13	)
Purchases		-			1			-			-			1
Settlements		4			39			-			-			43
Ending balance at June 30, 2011	$	(11	)	$	(106	)	$	-		$	-		$	(117	)
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2011	$	1		$	8		$	-		$	-		$	9
Power:
Beginning balance at January 1, 2011	$	2		$	(352	)	$	3		$	383		$	36
Realized and unrealized gains (losses):
Included in earnings(b)		-			-			(1	)		(17	)		(18	)
Included in OCI		-			-			-			5			5
Included in regulatory assets/liabilities		6			47			(a	)		11			64
Total realized and unrealized gains (losses)		6			47			(1	)		(1	)		51
Purchases		29			-			-			30			59
Sales		-			-			-			(16	)		(16	)
Settlements		(12	)		101			(1	)		(104	)		(16	)
Transfers into Level 3		(1	)		-			-			2			1
Transfers out of Level 3		1			-			-			1			2
Ending balance at June 30, 2011	$	25		$	(204	)	$	1		$	295		$	117
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2011	$	-		$	64		$	(1	)	$	(4	)	$	59

	Net derivative commodity contracts
Six Months	Ameren Missouri			Ameren Illinois			Genco			Other(c)			Ameren
Uranium:
Beginning balance at January 1, 2011	$	2		$	(a	)	$	(a	)	$	(a	)	$	2
Realized and unrealized gains (losses):
Included in regulatory assets/liabilities		(4	)		(a	)		(a	)		(a	)		(4	)
Total realized and unrealized gains (losses)		(4	)		(a	)		(a	)		(a	)		(4	)
Ending balance at June 30, 2011	$	(2	)	$	(a	)	$	(a	)	$	(a	)	$	(2	)
Change in unrealized gains (losses) related to assets/liabilities held at June 30, 2011	$	(2	)	$	(a	)	$	(a	)	$	(a	)	$	(2	)

(a) Not applicable.

(b) Net gains and losses on fuel oils and natural gas derivative commodity contracts are recorded in Operating Expenses - Fuel, while net gains and losses on power derivative commodity contracts are recorded in Operating Revenues - Electric.

(c) Includes amounts for Merchant Generation nonregistrant subsidiaries and intercompany eliminations, including the elimination of financial power contracts between Ameren Illinois and Marketing Company.

Schedule Of Transfers Between Fair Value Hierarchy Levels

	Three Months					Six Months
	2012			2011		2012			2011
Ameren - derivative commodity contracts:(a)
Transfers into Level 3 / Transfers out of Level 1 - Fuel oils	$	-		$	-	$	2		$	-
Transfers out of Level 3 / Transfers into Level 1 - Fuel oils		-			-		(1	)		-
Transfers out of Level 3 / Transfers into Level 2 - Natural gas		-			-		185			-
Transfers into Level 3 / Transfers out of Level 2 - Power		1			1		1			1
Transfers out of Level 3 / Transfers into Level 2 - Power		-			2		1			2
Net fair value of Level 3 transfers	$	1		$	3	$	188		$	3
Ameren Missouri - derivative commodity contracts:
Transfers into Level 3 / Transfers out of Level 1 - Fuel oils	$	-		$	-	$	2		$	-
Transfers out of Level 3 / Transfers into Level 2 - Natural gas		-			-		15			-
Transfers into Level 3 / Transfers out of Level 2 - Power		-			-		-			(1	)
Transfers out of Level 3 / Transfers into Level 2 - Power		(1	)		1		(2	)		1
Net fair value of Level 3 transfers	$	(1	)	$	1	$	15		$	-
Ameren Illinois - derivative commodity contracts:
Transfers out of Level 3 / Transfers into Level 2 - Natural gas	$	-		$	-	$	170		$	-
Genco - derivative commodity contracts:
Transfers out of Level 3 / Transfers into Level 1 - Fuel oils	$	-		$	-	$	(1	)	$	-

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

Schedule Of Carrying Amounts And Estimated Fair Values Of Long-Term Debt, Capital Lease Obligations And Preferred Stock

	June 30, 2012				December 31, 2011
	Carrying Amount		Fair Value		Carrying Amount		Fair Value
Ameren:(a)(b)
Long-term debt and capital lease obligations (including current portion)	$	6,857	$	7,766	$	6,856	$	7,800
Preferred stock		142		93		142		92
Ameren Missouri:
Long-term debt and capital lease obligations (including current portion)	$	3,950	$	4,619	$	3,950	$	4,541
Preferred stock		80		55		80		55
Ameren Illinois:
Long-term debt (including current portion)	$	1,658	$	1,984	$	1,658	$	1,943
Preferred stock		62		38		62		37
Genco:
Long-term debt (including current portion)	$	824	$	679	$	824	$	839

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

(b) Preferred stock not subject to mandatory redemption of the Ameren subsidiaries along with the 20% noncontrolling interest of EEI is recorded in Noncontrolling Interests on the balance sheet.