$AEE
AMEREN CORP Stock $aee

$aee Overview Financials Valuation SEC Filings Company Website

2010 Q4 Form 10-K Financial Statement

#000144530513000414 Filed on March 01, 2013

Income Statement

Concept	2010 Q4	2009 Q4
Revenue	$1.706B	$1.684B
YoY Change	1.31%	-11.74%
Cost Of Revenue	$393.0M	$427.0M
YoY Change	-7.96%	-29.54%
Gross Profit	$1.313B	$1.257B
YoY Change	4.46%	-3.46%
Gross Profit Margin	76.96%	74.64%
Selling, General & Admin
YoY Change
% of Gross Profit
Research & Development
YoY Change
% of Gross Profit
Depreciation & Amortization	$158.0M	$151.0M
YoY Change	4.64%	-14.69%
% of Gross Profit	12.03%	12.01%
Operating Expenses	$1.115B	$1.010B
YoY Change	10.4%	-5.78%
Operating Profit	$198.0M	$245.0M
YoY Change	-19.18%	6.52%
Interest Expense	-$120.0M	-$132.0M
YoY Change	-9.09%	21.1%
% of Operating Profit	-60.61%	-53.88%
Other Income/Expense, Net	$6.000M	$13.00M
YoY Change	-53.85%	30.0%
Pretax Income	$84.00M	$126.0M
YoY Change	-33.33%	77.46%
Income Tax	$30.00M	$44.00M
% Of Pretax Income	35.71%	34.92%
Net Earnings	$52.00M	$79.00M
YoY Change	-34.18%	38.6%
Net Earnings / Revenue	3.05%	4.69%
Basic Earnings Per Share
Diluted Earnings Per Share	$216.8K	$333.3K
COMMON SHARES
Basic Shares Outstanding
Diluted Shares Outstanding

Balance Sheet

Concept	2010 Q4	2009 Q4
SHORT-TERM ASSETS
Cash & Short-Term Investments	$545.0M	$622.0M
YoY Change	-12.38%	576.09%
Cash & Equivalents	$538.0M	$622.0M
Short-Term Investments
Other Short-Term Assets	$911.0M	$696.0M
YoY Change	30.89%	-17.44%
Inventory	$707.0M	$782.0M
Prepaid Expenses
Receivables	$517.0M	$424.0M
Other Receivables	$210.0M	$318.0M
Total Short-Term Assets	$2.890B	$2.842B
YoY Change	1.69%	8.97%
LONG-TERM ASSETS
Property, Plant & Equipment	$17.85B	$17.61B
YoY Change	1.38%	6.3%
Goodwill	$411.0M	$831.0M
YoY Change	-50.54%
Intangibles	$7.000M
YoY Change
Long-Term Investments	$337.0M	$293.0M
YoY Change	15.02%	22.59%
Other Assets	$2.013B	$1.997B
YoY Change	0.8%	-11.6%
Total Long-Term Assets	$20.62B	$20.86B
YoY Change	-1.15%	3.97%
TOTAL ASSETS
Total Short-Term Assets	$2.890B	$2.842B
Total Long-Term Assets	$20.62B	$20.86B
Total Assets	$23.51B	$23.70B
YoY Change	-0.81%	4.55%
SHORT-TERM LIABILITIES
YoY Change
Accounts Payable	$651.0M	$694.0M
YoY Change	-6.2%	-14.64%
Accrued Expenses	$107.0M	$110.0M
YoY Change	-2.73%	2.8%
Deferred Revenue
YoY Change
Short-Term Debt	$269.0M	$20.00M
YoY Change	1245.0%	-98.3%
Long-Term Debt Due	$155.0M	$204.0M
YoY Change	-24.02%	-46.32%
Total Short-Term Liabilities	$1.888B	$1.711B
YoY Change	10.34%	-44.39%
LONG-TERM LIABILITIES
Long-Term Debt	$7.313B	$7.941B
YoY Change	-7.91%	21.16%
Other Long-Term Liabilities	$3.454B	$3.342B
YoY Change	3.35%	-7.93%
Total Long-Term Liabilities	$10.77B	$11.28B
YoY Change	-4.57%	10.79%
TOTAL LIABILITIES
Total Short-Term Liabilities	$1.888B	$1.711B
Total Long-Term Liabilities	$10.77B	$11.28B
Total Liabilities	$15.78B	$15.85B
YoY Change	-0.41%	0.88%
SHAREHOLDERS EQUITY
Retained Earnings
YoY Change
Common Stock
YoY Change
Preferred Stock
YoY Change
Treasury Stock (at cost)
YoY Change
Treasury Stock Shares
Shareholders Equity	$7.730B	$7.856B
YoY Change
Total Liabilities & Shareholders Equity	$23.51B	$23.70B
YoY Change	-0.81%	4.55%

Cashflow Statement

Concept	2010 Q4	2009 Q4
OPERATING ACTIVITIES
Net Income	$52.00M	$79.00M
YoY Change	-34.18%	38.6%
Depreciation, Depletion And Amortization	$158.0M	$151.0M
YoY Change	4.64%	-14.69%
Cash From Operating Activities	$327.0M	$271.0M
YoY Change	20.66%	0.0%
INVESTING ACTIVITIES
Capital Expenditures	-$329.0M	-$440.0M
YoY Change	-25.23%	-25.68%
Acquisitions
YoY Change
Other Investing Activities	$9.000M	$4.000M
YoY Change	125.0%	-200.0%
Cash From Investing Activities	-$320.0M	-$436.0M
YoY Change	-26.61%	-26.85%
FINANCING ACTIVITIES
Cash Dividend Paid
YoY Change
Common Stock Issuance & Retirement, Net
YoY Change
Debt Paid & Issued, Net
YoY Change
Cash From Financing Activities	-70.00M	224.0M
YoY Change	-131.25%	6.16%
NET CHANGE
Cash From Operating Activities	327.0M	271.0M
Cash From Investing Activities	-320.0M	-436.0M
Cash From Financing Activities	-70.00M	224.0M
Net Change In Cash	-63.00M	59.00M
YoY Change	-206.78%	-151.75%
FREE CASH FLOW
Cash From Operating Activities	$327.0M	$271.0M
Capital Expenditures	-$329.0M	-$440.0M
Free Cash Flow	$656.0M	$711.0M
YoY Change	-7.74%	-17.61%

Facts In Submission

Frame	Concept Type	Concept / XBRL Key	Value	Unit
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CY2011Q4	us-gaap	Accounts Payable And Accrued Liabilities Current AccountsPayableAndAccruedLiabilitiesCurrent	693000000	USD
CY2011Q4	us-gaap	Accounts Receivable Net Current AccountsReceivableNetCurrent	473000000	USD
CY2012Q4	us-gaap	Accounts Receivable Net Current AccountsReceivableNetCurrent	401000000	USD
CY2012Q4	us-gaap	Accumulated Deferred Investment Tax Credit AccumulatedDeferredInvestmentTaxCredit	72000000	USD
CY2011Q4	us-gaap	Accumulated Deferred Investment Tax Credit AccumulatedDeferredInvestmentTaxCredit	79000000	USD
CY2011Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	9429000000	USD
CY2012Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	8823000000	USD
CY2012Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-8000000	USD
CY2011Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-50000000	USD
CY2011Q4	us-gaap	Additional Collateral Aggregate Fair Value AdditionalCollateralAggregateFairValue	332000000	USD
CY2012Q4	us-gaap	Additional Collateral Aggregate Fair Value AdditionalCollateralAggregateFairValue	245000000	USD
CY2012Q4	us-gaap	Additional Paid In Capital AdditionalPaidInCapital	5616000000	USD
CY2011Q4	us-gaap	Additional Paid In Capital AdditionalPaidInCapital	5598000000	USD
CY2010	us-gaap	Adjustment For Amortization AdjustmentForAmortization	54000000	USD
CY2011	us-gaap	Adjustment For Amortization AdjustmentForAmortization	61000000	USD
CY2012	us-gaap	Adjustment For Amortization AdjustmentForAmortization	83000000	USD
CY2010	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	13000000	USD
CY2011	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	14000000	USD
CY2012	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	24000000	USD
CY2012Q4	us-gaap	Allowance For Doubtful Accounts Receivable Current AllowanceForDoubtfulAccountsReceivableCurrent	17000000	USD
CY2011Q4	us-gaap	Allowance For Doubtful Accounts Receivable Current AllowanceForDoubtfulAccountsReceivableCurrent	20000000	USD
CY2011	us-gaap	Amortization Of Financing Costs And Discounts AmortizationOfFinancingCostsAndDiscounts	21000000	USD
CY2012	us-gaap	Amortization Of Financing Costs And Discounts AmortizationOfFinancingCostsAndDiscounts	24000000	USD
CY2010	us-gaap	Amortization Of Financing Costs And Discounts AmortizationOfFinancingCostsAndDiscounts	23000000	USD
CY2012	us-gaap	Asset Impairment Charges AssetImpairmentCharges	2578000000	USD
CY2011	us-gaap	Asset Impairment Charges AssetImpairmentCharges	125000000	USD
CY2010	us-gaap	Asset Impairment Charges AssetImpairmentCharges	589000000	USD
CY2012Q4	us-gaap	Asset Retirement Obligation AssetRetirementObligation	453000000	USD
CY2010Q4	us-gaap	Asset Retirement Obligation AssetRetirementObligation	475000000	USD
CY2011Q4	us-gaap	Asset Retirement Obligation AssetRetirementObligation	433000000	USD
CY2011	us-gaap	Asset Retirement Obligation Accretion Expense AssetRetirementObligationAccretionExpense	27000000	USD
CY2012	us-gaap	Asset Retirement Obligation Accretion Expense AssetRetirementObligationAccretionExpense	24000000	USD
CY2012Q4	us-gaap	Asset Retirement Obligation Current AssetRetirementObligationCurrent	8000000	USD
CY2011Q4	us-gaap	Asset Retirement Obligation Current AssetRetirementObligationCurrent	5000000	USD
CY2012	us-gaap	Asset Retirement Obligation Liabilities Incurred AssetRetirementObligationLiabilitiesIncurred	2000000	USD
CY2011	us-gaap	Asset Retirement Obligation Liabilities Incurred AssetRetirementObligationLiabilitiesIncurred	1000000	USD
CY2011	us-gaap	Asset Retirement Obligation Liabilities Settled AssetRetirementObligationLiabilitiesSettled	3000000	USD
CY2012	us-gaap	Asset Retirement Obligation Liabilities Settled AssetRetirementObligationLiabilitiesSettled	6000000	USD
CY2011	us-gaap	Asset Retirement Obligation Revision Of Estimate AssetRetirementObligationRevisionOfEstimate	-66000000	USD
CY2012	us-gaap	Asset Retirement Obligation Revision Of Estimate AssetRetirementObligationRevisionOfEstimate	1000000	USD
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CY2011Q4	us-gaap	Asset Retirement Obligations Noncurrent AssetRetirementObligationsNoncurrent	428000000	USD
CY2012Q4	us-gaap	Assets Assets	21835000000	USD
CY2011Q4	us-gaap	Assets Assets	23645000000	USD
CY2010Q4	us-gaap	Assets Assets	23511000000	USD
CY2012Q4	us-gaap	Assets Current AssetsCurrent	2369000000	USD
CY2011Q4	us-gaap	Assets Current AssetsCurrent	2295000000	USD
CY2011Q4	us-gaap	Assets Fair Value Disclosure AssetsFairValueDisclosure	596000000	USD
CY2012Q4	us-gaap	Assets Fair Value Disclosure AssetsFairValueDisclosure	568000000	USD
CY2011Q4	us-gaap	Available For Sale Securities AvailableForSaleSecurities	261000000	USD
CY2012Q4	us-gaap	Available For Sale Securities AvailableForSaleSecurities	281000000	USD
CY2012Q4	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position Fair Value AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue	38000000	USD
CY2012Q4	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue	24000000	USD
CY2012Q4	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue	14000000	USD
CY2012Q4	us-gaap	Available For Sale Securities Debt Maturities After Five Through Ten Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsAmortizedCost	32000000	USD
CY2012Q4	us-gaap	Available For Sale Securities Debt Maturities After Five Through Ten Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue	35000000	USD
CY2012Q4	us-gaap	Available For Sale Securities Debt Maturities After One Through Five Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost	78000000	USD
CY2012Q4	us-gaap	Available For Sale Securities Debt Maturities After One Through Five Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue	79000000	USD
CY2012Q4	us-gaap	Available For Sale Securities Debt Maturities After Ten Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsAmortizedCost	23000000	USD
CY2012Q4	us-gaap	Available For Sale Securities Debt Maturities After Ten Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue	27000000	USD
CY2012Q4	us-gaap	Available For Sale Securities Debt Maturities Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAmortizedCost	133000000	USD
CY2012Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	141000000	USD
CY2011	us-gaap	Available For Sale Securities Gross Realized Gains AvailableForSaleSecuritiesGrossRealizedGains	5000000	USD
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CY2012	us-gaap	Available For Sale Securities Gross Realized Gains AvailableForSaleSecuritiesGrossRealizedGains	6000000	USD
CY2012	us-gaap	Available For Sale Securities Gross Realized Losses AvailableForSaleSecuritiesGrossRealizedLosses	2000000	USD
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CY2010	us-gaap	Available For Sale Securities Gross Realized Losses AvailableForSaleSecuritiesGrossRealizedLosses	4000000	USD
CY2011Q4	us-gaap	Available For Sale Securities Gross Unrealized Losses1 AvailableForSaleSecuritiesGrossUnrealizedLosses1	12000000	USD
CY2012Q4	us-gaap	Available For Sale Securities Gross Unrealized Losses1 AvailableForSaleSecuritiesGrossUnrealizedLosses1	11000000	USD
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CY2012Q4	us-gaap	Availableforsale Securities Continuous Unrealized Loss Position Aggregate Losses2 AvailableforsaleSecuritiesContinuousUnrealizedLossPositionAggregateLosses2	11000000	USD
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CY2012Q4	us-gaap	Capital Leased Assets Gross CapitalLeasedAssetsGross	228000000	USD
CY2012Q4	us-gaap	Capital Leases Future Minimum Payments Due CapitalLeasesFutureMinimumPaymentsDue	588000000	USD
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CY2012Q4	us-gaap	Capital Leases Future Minimum Payments Due In Five Years CapitalLeasesFutureMinimumPaymentsDueInFiveYears	33000000	USD
CY2012Q4	us-gaap	Capital Leases Future Minimum Payments Due In Four Years CapitalLeasesFutureMinimumPaymentsDueInFourYears	33000000	USD
CY2012Q4	us-gaap	Capital Leases Future Minimum Payments Due In Three Years CapitalLeasesFutureMinimumPaymentsDueInThreeYears	33000000	USD
CY2012Q4	us-gaap	Capital Leases Future Minimum Payments Due In Two Years CapitalLeasesFutureMinimumPaymentsDueInTwoYears	32000000	USD
CY2012Q4	us-gaap	Capital Leases Future Minimum Payments Due Thereafter CapitalLeasesFutureMinimumPaymentsDueThereafter	425000000	USD
CY2012Q4	us-gaap	Capital Leases Future Minimum Payments Interest Included In Payments CapitalLeasesFutureMinimumPaymentsInterestIncludedInPayments	284000000	USD
CY2012Q4	us-gaap	Capital Leases Future Minimum Payments Present Value Of Net Minimum Payments CapitalLeasesFutureMinimumPaymentsPresentValueOfNetMinimumPayments	304000000	USD
CY2012Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	209000000	USD
CY2011Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	255000000	USD
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CY2012Q4	us-gaap	Collateral Already Posted Aggregate Fair Value CollateralAlreadyPostedAggregateFairValue	68000000	USD
CY2011Q4	us-gaap	Collateral Already Posted Aggregate Fair Value CollateralAlreadyPostedAggregateFairValue	116000000	USD
CY2011Q4	us-gaap	Commitments And Contingencies CommitmentsAndContingencies		USD
CY2012Q4	us-gaap	Commitments And Contingencies CommitmentsAndContingencies		USD
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CY2011Q4	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	400000000	shares
CY2012Q4	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	400000000	shares
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CY2012Q4	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	242600000	shares
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CY2010Q4	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	240400000	shares
CY2011Q4	us-gaap	Common Stock Value CommonStockValue	2000000	USD
CY2012Q4	us-gaap	Common Stock Value CommonStockValue	2000000	USD
CY2010	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	135000000	USD
CY2011	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	486000000	USD
CY2012	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	-932000000	USD
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CY2012	us-gaap	Cost Of Goods Sold Depreciation Depletion And Amortization CostOfGoodsSoldDepreciationDepletionAndAmortization	775000000	USD
CY2010	us-gaap	Cost Of Natural Gas Purchases CostOfNaturalGasPurchases	669000000	USD
CY2011	us-gaap	Cost Of Natural Gas Purchases CostOfNaturalGasPurchases	570000000	USD
CY2012	us-gaap	Cost Of Natural Gas Purchases CostOfNaturalGasPurchases	472000000	USD
CY2010	us-gaap	Cost Of Purchased Power CostOfPurchasedPower	1106000000	USD
CY2011	us-gaap	Cost Of Purchased Power CostOfPurchasedPower	966000000	USD
CY2012	us-gaap	Cost Of Purchased Power CostOfPurchasedPower	654000000	USD
CY2010	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	13000000	USD
CY2012	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	31000000	USD
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CY2011Q4	us-gaap	Customer Deposits Current CustomerDepositsCurrent	98000000	USD
CY2011Q4	us-gaap	Decommissioning Fund Investments DecommissioningFundInvestments	357000000	USD
CY2012Q4	us-gaap	Decommissioning Fund Investments DecommissioningFundInvestments	408000000	USD
CY2011Q4	us-gaap	Decommissioning Trust Assets Amount DecommissioningTrustAssetsAmount	358000000	USD
CY2012Q4	us-gaap	Decommissioning Trust Assets Amount DecommissioningTrustAssetsAmount	406000000	USD
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CY2011	us-gaap	Deferred Income Taxes And Tax Credits DeferredIncomeTaxesAndTaxCredits	346000000	USD
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CY2011	us-gaap	Deferred Other Tax Expense Benefit DeferredOtherTaxExpenseBenefit	-7000000	USD
CY2012	us-gaap	Deferred Other Tax Expense Benefit DeferredOtherTaxExpenseBenefit	-7000000	USD
CY2012	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	-117000000	USD
CY2010	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	36000000	USD
CY2011	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	76000000	USD
CY2011Q4	us-gaap	Deferred Tax Assets Net Current DeferredTaxAssetsNetCurrent	20000000	USD
CY2012Q4	us-gaap	Deferred Tax Assets Net Current DeferredTaxAssetsNetCurrent	171000000	USD
CY2012Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefits	337000000	USD
CY2011Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefits	367000000	USD
CY2012Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Asset Retirement Obligations DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAssetRetirementObligations	44000000	USD
CY2011Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Asset Retirement Obligations DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAssetRetirementObligations	37000000	USD
CY2012Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Impairment Losses DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsImpairmentLosses	986000000	USD
CY2011Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Impairment Losses DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsImpairmentLosses	15000000	USD
CY2011Q4	us-gaap	Deferred Tax Liabilities DeferredTaxLiabilities	3295000000	USD
CY2012Q4	us-gaap	Deferred Tax Liabilities DeferredTaxLiabilities	2621000000	USD
CY2011Q4	us-gaap	Deferred Tax Liabilities Goodwill And Intangible Assets DeferredTaxLiabilitiesGoodwillAndIntangibleAssets	35000000	USD
CY2012Q4	us-gaap	Deferred Tax Liabilities Goodwill And Intangible Assets DeferredTaxLiabilitiesGoodwillAndIntangibleAssets	-10000000	USD
CY2011Q4	us-gaap	Deferred Tax Liabilities Noncurrent DeferredTaxLiabilitiesNoncurrent	3315000000	USD
CY2012Q4	us-gaap	Deferred Tax Liabilities Noncurrent DeferredTaxLiabilitiesNoncurrent	2792000000	USD
CY2011Q4	us-gaap	Deferred Tax Liabilities Other DeferredTaxLiabilitiesOther	-223000000	USD
CY2012Q4	us-gaap	Deferred Tax Liabilities Other DeferredTaxLiabilitiesOther	-278000000	USD
CY2011Q4	us-gaap	Deferred Tax Liabilities Property Plant And Equipment DeferredTaxLiabilitiesPropertyPlantAndEquipment	3826000000	USD
CY2012Q4	us-gaap	Deferred Tax Liabilities Property Plant And Equipment DeferredTaxLiabilitiesPropertyPlantAndEquipment	4201000000	USD
CY2011Q4	us-gaap	Deferred Tax Liabilities Regulatory Assets And Liabilities DeferredTaxLiabilitiesRegulatoryAssetsAndLiabilities	73000000	USD
CY2012Q4	us-gaap	Deferred Tax Liabilities Regulatory Assets And Liabilities DeferredTaxLiabilitiesRegulatoryAssetsAndLiabilities	73000000	USD
CY2010	us-gaap	Depreciation Amortization And Accretion Net DepreciationAmortizationAndAccretionNet	746000000	USD
CY2011	us-gaap	Depreciation Amortization And Accretion Net DepreciationAmortizationAndAccretionNet	747000000	USD
CY2012	us-gaap	Depreciation Amortization And Accretion Net DepreciationAmortizationAndAccretionNet	735000000	USD
CY2012Q4	us-gaap	Derivative Collateral Obligation To Return Cash DerivativeCollateralObligationToReturnCash	3000000	USD
CY2011Q4	us-gaap	Derivative Collateral Obligation To Return Cash DerivativeCollateralObligationToReturnCash	1000000	USD
CY2012Q4	us-gaap	Derivative Credit Risk Valuation Adjustment Derivative Liabilities DerivativeCreditRiskValuationAdjustmentDerivativeLiabilities	7000000	USD
CY2011Q4	us-gaap	Derivative Credit Risk Valuation Adjustment Derivative Liabilities DerivativeCreditRiskValuationAdjustmentDerivativeLiabilities	1000000	USD
CY2012Q4	us-gaap	Derivative Instruments And Hedges DerivativeInstrumentsAndHedges	125000000	USD
CY2011Q4	us-gaap	Derivative Instruments And Hedges DerivativeInstrumentsAndHedges	115000000	USD
CY2011Q4	us-gaap	Derivative Net Liability Position Aggregate Fair Value DerivativeNetLiabilityPositionAggregateFairValue	456000000	USD
CY2012Q4	us-gaap	Derivative Net Liability Position Aggregate Fair Value DerivativeNetLiabilityPositionAggregateFairValue	356000000	USD
CY2011Q4	us-gaap	Dividends Payable Current And Noncurrent DividendsPayableCurrentAndNoncurrent		USD
CY2010Q4	us-gaap	Dividends Payable Current And Noncurrent DividendsPayableCurrentAndNoncurrent		USD
CY2012Q4	us-gaap	Dividends Payable Current And Noncurrent DividendsPayableCurrentAndNoncurrent	7000000	USD
CY2010	us-gaap	Earnings Per Share Basic And Diluted EarningsPerShareBasicAndDiluted	0.58
CY2011	us-gaap	Earnings Per Share Basic And Diluted EarningsPerShareBasicAndDiluted	2.15
CY2012	us-gaap	Earnings Per Share Basic And Diluted EarningsPerShareBasicAndDiluted	-4.01
CY2011Q3	us-gaap	Earnings Per Share Basic And Diluted EarningsPerShareBasicAndDiluted	1.18
CY2011Q2	us-gaap	Earnings Per Share Basic And Diluted EarningsPerShareBasicAndDiluted	0.57
CY2012Q2	us-gaap	Earnings Per Share Basic And Diluted EarningsPerShareBasicAndDiluted	0.87
CY2011Q1	us-gaap	Earnings Per Share Basic And Diluted EarningsPerShareBasicAndDiluted	0.29
CY2012Q4	us-gaap	Earnings Per Share Basic And Diluted EarningsPerShareBasicAndDiluted	-4.76
CY2012Q1	us-gaap	Earnings Per Share Basic And Diluted EarningsPerShareBasicAndDiluted	-1.66
CY2011Q4	us-gaap	Earnings Per Share Basic And Diluted EarningsPerShareBasicAndDiluted	0.10
CY2012Q3	us-gaap	Earnings Per Share Basic And Diluted EarningsPerShareBasicAndDiluted	1.54
CY2011	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.37
CY2012	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.41
CY2010	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.68
CY2011	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.35
CY2010	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.35
CY2012	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.35
CY2010	us-gaap	Effective Income Tax Rate Reconciliation Change In Enacted Tax Rate EffectiveIncomeTaxRateReconciliationChangeInEnactedTaxRate	0.03
CY2011	us-gaap	Effective Income Tax Rate Reconciliation Deductions EffectiveIncomeTaxRateReconciliationDeductions
CY2012	us-gaap	Fuel Costs FuelCosts	1369000000	USD
CY2010	us-gaap	Fuel Costs FuelCosts	1323000000	USD
CY2011	us-gaap	Fuel Costs FuelCosts	1567000000	USD
CY2010	us-gaap	Effective Income Tax Rate Reconciliation Nondeductible Expense Depreciation EffectiveIncomeTaxRateReconciliationNondeductibleExpenseDepreciation	-0.04
CY2011	us-gaap	Effective Income Tax Rate Reconciliation Nondeductible Expense Depreciation EffectiveIncomeTaxRateReconciliationNondeductibleExpenseDepreciation	-0.01
CY2012	us-gaap	Effective Income Tax Rate Reconciliation Nondeductible Expense Depreciation EffectiveIncomeTaxRateReconciliationNondeductibleExpenseDepreciation
CY2010	us-gaap	Effective Income Tax Rate Reconciliation Nondeductible Expense Impairment Losses EffectiveIncomeTaxRateReconciliationNondeductibleExpenseImpairmentLosses	0.32
CY2010	us-gaap	Effective Income Tax Rate Reconciliation State And Local Income Taxes EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes	0.08
CY2011	us-gaap	Effective Income Tax Rate Reconciliation State And Local Income Taxes EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes	0.04
CY2012	us-gaap	Effective Income Tax Rate Reconciliation State And Local Income Taxes EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes	0.05
CY2012	us-gaap	Effective Income Tax Rate Reconciliation Tax Contingencies EffectiveIncomeTaxRateReconciliationTaxContingencies
CY2010	us-gaap	Effective Income Tax Rate Reconciliation Tax Contingencies EffectiveIncomeTaxRateReconciliationTaxContingencies	-0.01
CY2010	us-gaap	Effective Income Tax Rate Reconciliation Tax Credits EffectiveIncomeTaxRateReconciliationTaxCredits	-0.03
CY2012	us-gaap	Effective Income Tax Rate Reconciliation Tax Credits Investment EffectiveIncomeTaxRateReconciliationTaxCreditsInvestment	0.01
CY2011	us-gaap	Effective Income Tax Rate Reconciliation Tax Credits Investment EffectiveIncomeTaxRateReconciliationTaxCreditsInvestment	-0.01
CY2010	us-gaap	Effective Income Tax Rate Reconciliation Tax Credits Investment EffectiveIncomeTaxRateReconciliationTaxCreditsInvestment	-0.02
CY2010	us-gaap	Electric Utility Revenue ElectricUtilityRevenue	6521000000	USD
CY2011	us-gaap	Electric Utility Revenue ElectricUtilityRevenue	6530000000	USD
CY2012	us-gaap	Electric Utility Revenue ElectricUtilityRevenue	5904000000	USD
CY2010	us-gaap	Employee Service Share Based Compensation Cash Flow Effect Cash Used To Settle Awards EmployeeServiceShareBasedCompensationCashFlowEffectCashUsedToSettleAwards	2000000	USD
CY2011	us-gaap	Employee Service Share Based Compensation Cash Flow Effect Cash Used To Settle Awards EmployeeServiceShareBasedCompensationCashFlowEffectCashUsedToSettleAwards	4000000	USD
CY2012	us-gaap	Employee Service Share Based Compensation Cash Flow Effect Cash Used To Settle Awards EmployeeServiceShareBasedCompensationCashFlowEffectCashUsedToSettleAwards	11000000	USD
CY2012Q4	us-gaap	Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized	21000000	USD
CY2012	us-gaap	Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized Period For Recognition1 EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1	P20M
CY2010	us-gaap	Employee Service Share Based Compensation Tax Benefit From Compensation Expense EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense	5000000	USD
CY2012	us-gaap	Employee Service Share Based Compensation Tax Benefit From Compensation Expense EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense	9000000	USD
CY2011	us-gaap	Employee Service Share Based Compensation Tax Benefit From Compensation Expense EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense	5000000	USD
CY2011Q4	us-gaap	Energy Related Inventory Coal EnergyRelatedInventoryCoal	251000000	USD
CY2012Q4	us-gaap	Energy Related Inventory Coal EnergyRelatedInventoryCoal	276000000	USD
CY2012Q4	us-gaap	Energy Related Inventory Gas Stored Underground EnergyRelatedInventoryGasStoredUnderground	131000000	USD
CY2011Q4	us-gaap	Energy Related Inventory Gas Stored Underground EnergyRelatedInventoryGasStoredUnderground	171000000	USD
CY2011	us-gaap	Excise And Sales Taxes ExciseAndSalesTaxes	194000000	USD
CY2010	us-gaap	Excise And Sales Taxes ExciseAndSalesTaxes	189000000	USD
CY2012	us-gaap	Excise And Sales Taxes ExciseAndSalesTaxes	193000000	USD
CY2013Q1	us-gaap	Former Gain Contingency Recognized In Current Period FormerGainContingencyRecognizedInCurrentPeriod	5000000	USD
CY2011Q4	us-gaap	Former Gain Contingency Recognized In Current Period FormerGainContingencyRecognizedInCurrentPeriod	11000000	USD
CY2011	us-gaap	Gain Loss On Sale Of Properties GainLossOnSaleOfProperties	15000000	USD
CY2010	us-gaap	Gain Loss On Sale Of Properties GainLossOnSaleOfProperties	10000000	USD
CY2012	us-gaap	Gain Loss On Sale Of Properties GainLossOnSaleOfProperties	11000000	USD
CY2012	us-gaap	Gas Domestic Regulated Revenue GasDomesticRegulatedRevenue	924000000	USD
CY2011	us-gaap	Gas Domestic Regulated Revenue GasDomesticRegulatedRevenue	1001000000	USD
CY2010	us-gaap	Gas Domestic Regulated Revenue GasDomesticRegulatedRevenue	1117000000	USD
CY2012Q4	us-gaap	Goodwill Goodwill	411000000	USD
CY2011Q4	us-gaap	Goodwill Goodwill	411000000	USD
CY2012	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	0	USD
CY2011	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	0	USD
CY2010	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	420000000	USD
CY2012Q4	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	304000000	USD
CY2011Q4	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	309000000	USD
CY2010	us-gaap	Impairment Of Intangible Assets Finitelived ImpairmentOfIntangibleAssetsFinitelived	68000000	USD
CY2012	us-gaap	Impairment Of Intangible Assets Finitelived ImpairmentOfIntangibleAssetsFinitelived	0	USD
CY2011	us-gaap	Impairment Of Intangible Assets Finitelived ImpairmentOfIntangibleAssetsFinitelived	2000000	USD
CY2010	us-gaap	Impairment Of Long Lived Assets Held For Use ImpairmentOfLongLivedAssetsHeldForUse	101000000	USD
CY2012	us-gaap	Impairment Of Long Lived Assets Held For Use ImpairmentOfLongLivedAssetsHeldForUse	2578000000	USD
CY2011	us-gaap	Impairment Of Long Lived Assets Held For Use ImpairmentOfLongLivedAssetsHeldForUse	123000000	USD
CY2012	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	-1654000000	USD
CY2010	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	476000000	USD
CY2011	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	836000000	USD
CY2012	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	-680000000	USD
CY2011	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	310000000	USD
CY2010	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	325000000	USD
CY2010	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	-92000000	USD
CY2012	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	1000000	USD
CY2011	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	-61000000	USD
CY2010	us-gaap	Increase Decrease In Accounts Payable And Accrued Liabilities IncreaseDecreaseInAccountsPayableAndAccruedLiabilities	20000000	USD
CY2012	us-gaap	Increase Decrease In Accounts Payable And Accrued Liabilities IncreaseDecreaseInAccountsPayableAndAccruedLiabilities	-29000000	USD
CY2011	us-gaap	Increase Decrease In Accounts Payable And Accrued Liabilities IncreaseDecreaseInAccountsPayableAndAccruedLiabilities	-36000000	USD
CY2010	us-gaap	Increase Decrease In Accrued Taxes Payable IncreaseDecreaseInAccruedTaxesPayable	10000000	USD
CY2012	us-gaap	Increase Decrease In Accrued Taxes Payable IncreaseDecreaseInAccruedTaxesPayable	3000000	USD
CY2011	us-gaap	Increase Decrease In Accrued Taxes Payable IncreaseDecreaseInAccruedTaxesPayable	-3000000	USD
CY2011	us-gaap	Increase Decrease In Deposit Other Assets IncreaseDecreaseInDepositOtherAssets	-27000000	USD
CY2012	us-gaap	Increase Decrease In Deposit Other Assets IncreaseDecreaseInDepositOtherAssets	-46000000	USD
CY2010	us-gaap	Increase Decrease In Deposit Other Assets IncreaseDecreaseInDepositOtherAssets	73000000	USD
CY2011	us-gaap	Increase Decrease In Employee Related Liabilities IncreaseDecreaseInEmployeeRelatedLiabilities	-102000000	USD
CY2010	us-gaap	Increase Decrease In Employee Related Liabilities IncreaseDecreaseInEmployeeRelatedLiabilities	-5000000	USD
CY2012	us-gaap	Increase Decrease In Employee Related Liabilities IncreaseDecreaseInEmployeeRelatedLiabilities	-23000000	USD
CY2012	us-gaap	Increase Decrease In Insurance Settlements Receivable IncreaseDecreaseInInsuranceSettlementsReceivable		USD
CY2010	us-gaap	Increase Decrease In Insurance Settlements Receivable IncreaseDecreaseInInsuranceSettlementsReceivable	-54000000	USD
CY2011	us-gaap	Increase Decrease In Insurance Settlements Receivable IncreaseDecreaseInInsuranceSettlementsReceivable	1000000	USD
CY2010	us-gaap	Increase Decrease In Inventories IncreaseDecreaseInInventories	-73000000	USD
CY2011	us-gaap	Increase Decrease In Inventories IncreaseDecreaseInInventories	27000000	USD
CY2012	us-gaap	Increase Decrease In Inventories IncreaseDecreaseInInventories	-5000000	USD
CY2010	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	47000000	USD
CY2011	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	-76000000	USD
CY2012	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	10000000	USD
CY2010	us-gaap	Increase Decrease In Other Operating Liabilities IncreaseDecreaseInOtherOperatingLiabilities	71000000	USD
CY2011	us-gaap	Increase Decrease In Other Operating Liabilities IncreaseDecreaseInOtherOperatingLiabilities	-75000000	USD
CY2012	us-gaap	Increase Decrease In Other Operating Liabilities IncreaseDecreaseInOtherOperatingLiabilities	71000000	USD
CY2012	us-gaap	Increase Decrease In Receivables IncreaseDecreaseInReceivables	-33000000	USD
CY2010	us-gaap	Increase Decrease In Receivables IncreaseDecreaseInReceivables	197000000	USD
CY2011	us-gaap	Increase Decrease In Receivables IncreaseDecreaseInReceivables	-231000000	USD
CY2012Q4	us-gaap	Intangible Assets Net Excluding Goodwill IntangibleAssetsNetExcludingGoodwill	16000000	USD
CY2011Q4	us-gaap	Intangible Assets Net Excluding Goodwill IntangibleAssetsNetExcludingGoodwill	7000000	USD
CY2010	us-gaap	Interest Expense InterestExpense	497000000	USD
CY2011	us-gaap	Interest Expense InterestExpense	451000000	USD
CY2012	us-gaap	Interest Expense InterestExpense	448000000	USD
CY2011	us-gaap	Interest Income Securities Tax Exempt InterestIncomeSecuritiesTaxExempt	28000000	USD
CY2012	us-gaap	Interest Income Securities Tax Exempt InterestIncomeSecuritiesTaxExempt	28000000	USD
CY2010	us-gaap	Interest Income Securities Tax Exempt InterestIncomeSecuritiesTaxExempt	28000000	USD
CY2011	us-gaap	Interest Paid Capitalized InterestPaidCapitalized	30000000	USD
CY2010	us-gaap	Interest Paid Capitalized InterestPaidCapitalized	34000000	USD
CY2012	us-gaap	Interest Paid Capitalized InterestPaidCapitalized	30000000	USD
CY2011	us-gaap	Interest Paid Net InterestPaidNet	453000000	USD
CY2010	us-gaap	Interest Paid Net InterestPaidNet	494000000	USD
CY2012	us-gaap	Interest Paid Net InterestPaidNet	433000000	USD
CY2011Q4	us-gaap	Interest Payable Current InterestPayableCurrent	101000000	USD
CY2012Q4	us-gaap	Interest Payable Current InterestPayableCurrent	99000000	USD
CY2012Q4	us-gaap	Inventory Net InventoryNet	704000000	USD
CY2012	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-1310000000	USD
CY2010	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-1096000000	USD
CY2011Q4	us-gaap	Inventory Net InventoryNet	712000000	USD
CY2010	us-gaap	Investment Income Interest And Dividend InvestmentIncomeInterestAndDividend	33000000	USD
CY2011	us-gaap	Investment Income Interest And Dividend InvestmentIncomeInterestAndDividend	32000000	USD
CY2012	us-gaap	Investment Income Interest And Dividend InvestmentIncomeInterestAndDividend	33000000	USD
CY2011	us-gaap	Lease And Rental Expense LeaseAndRentalExpense	47000000	USD
CY2012	us-gaap	Lease And Rental Expense LeaseAndRentalExpense	48000000	USD
CY2010	us-gaap	Lease And Rental Expense LeaseAndRentalExpense	52000000	USD
CY2012Q4	us-gaap	Letters Of Credit Outstanding Amount LettersOfCreditOutstandingAmount	9000000	USD
CY2012Q4	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	21835000000	USD
CY2011Q4	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	23645000000	USD
CY2011Q4	us-gaap	Liabilities Current LiabilitiesCurrent	1785000000	USD
CY2012Q4	us-gaap	Liabilities Current LiabilitiesCurrent	1698000000	USD
CY2011Q4	us-gaap	Liabilities Other Than Longterm Debt Noncurrent LiabilitiesOtherThanLongtermDebtNoncurrent	7115000000	USD
CY2012Q4	us-gaap	Liabilities Other Than Longterm Debt Noncurrent LiabilitiesOtherThanLongtermDebtNoncurrent	6744000000	USD
CY2012Q2	us-gaap	Liability For Uncertain Tax Positions Current LiabilityForUncertainTaxPositionsCurrent	39000000	USD
CY2012Q4	us-gaap	Long Term Debt LongTermDebt	6992000000	USD
CY2012Q4	us-gaap	Long Term Debt Current LongTermDebtCurrent	355000000	USD
CY2011Q4	us-gaap	Long Term Debt Current LongTermDebtCurrent	179000000	USD
CY2012Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal After Year Five LongTermDebtMaturitiesRepaymentsOfPrincipalAfterYearFive	4907000000	USD
CY2012Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Next Twelve Months LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths	355000000	USD
CY2012Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Five LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive	681000000	USD
CY2012Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Four LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour	395000000	USD
CY2012Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Three LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree	120000000	USD
CY2012Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Two LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo	534000000	USD
CY2011Q4	us-gaap	Long Term Debt Noncurrent LongTermDebtNoncurrent	6677000000	USD
CY2012Q4	us-gaap	Long Term Debt Noncurrent LongTermDebtNoncurrent	6626000000	USD
CY2011Q4	us-gaap	Minority Interest MinorityInterest	149000000	USD
CY2012Q4	us-gaap	Minority Interest MinorityInterest	151000000	USD
CY2012	us-gaap	Nature Of Operations NatureOfOperations	<div style="font-family:Times New Roman;font-size:10pt;"><div style="line-height:120%;padding-top:13px;text-indent:24px;font-size:10pt;"><font style="font-family:Arial Narrow;font-size:10pt;">Ameren, headquartered in St. Louis, Missouri, is a public utility holding company under PUHCA 2005, administered by FERC. Ameren’s primary assets are its equity interests in its subsidiaries. Ameren’s subsidiaries are separate, independent legal entities with separate businesses, assets, and liabilities. These subsidiaries operate, as the case may be, rate-regulated electric generation, transmission and distribution businesses, rate-regulated natural gas transmission and distribution businesses, and merchant electric generation businesses. Dividends on Ameren’s common stock and the payment of other expenses by Ameren depend on distributions made to it by its subsidiaries. Ameren’s principal subsidiaries are listed below. </font></div><table cellpadding="0" cellspacing="0" style="padding-top:13px;font-family:Times New Roman; font-size:10pt;"><tr><td style="width:24px;" rowspan="1" colspan="1"></td><td rowspan="1" colspan="1"></td></tr><tr><td style="vertical-align:top" rowspan="1" colspan="1"><div style="line-height:120%;font-size:10pt;padding-left:0px;"><font style="font-family:Arial Narrow;font-size:10pt;">•</font></div></td><td style="vertical-align:top;" rowspan="1" colspan="1"><div style="line-height:120%;font-size:10pt;"><font style="font-family:Arial Narrow;font-size:10pt;">Union Electric Company, or Ameren Missouri, operates a rate-regulated electric generation, transmission, and distribution business, and a rate-regulated natural gas transmission and distribution business in Missouri. Ameren Missouri was incorporated in Missouri in 1922 and is successor to a number of companies, the oldest of which was organized in 1881. It is the largest electric utility in the state of Missouri. It supplies electric and natural gas service to a </font><font style="font-family:Arial Narrow;font-size:10pt;color:#000000;text-decoration:none;">24,000</font><font style="font-family:Arial Narrow;font-size:10pt;">-square-mile area in central and eastern Missouri. This area has an estimated population of </font><font style="font-family:Arial Narrow;font-size:10pt;color:#000000;text-decoration:none;">2.8 million</font><font style="font-family:Arial Narrow;font-size:10pt;"> and includes the Greater St. Louis area. Ameren Missouri supplies electric service to </font><font style="font-family:Arial Narrow;font-size:10pt;color:#000000;text-decoration:none;">1.2 million</font><font style="font-family:Arial Narrow;font-size:10pt;"> customers and natural gas service to </font><font style="font-family:Arial Narrow;font-size:10pt;color:#000000;text-decoration:none;">127,000</font><font style="font-family:Arial Narrow;font-size:10pt;"> customers.</font></div></td></tr></table><table cellpadding="0" cellspacing="0" style="font-family:Times New Roman; font-size:10pt;"><tr><td style="width:24px;" rowspan="1" colspan="1"></td><td rowspan="1" colspan="1"></td></tr><tr><td style="vertical-align:top" rowspan="1" colspan="1"><div style="line-height:120%;font-size:10pt;padding-left:0px;"><font style="font-family:Arial Narrow;font-size:10pt;">•</font></div></td><td style="vertical-align:top;" rowspan="1" colspan="1"><div style="line-height:120%;font-size:10pt;"><font style="font-family:Arial Narrow;font-size:10pt;">Ameren Illinois Company, or Ameren Illinois, operates a rate-regulated electric and natural gas transmission and distribution business in Illinois. Ameren Illinois was created by the merger of CILCO and IP with and into CIPS. CIPS was incorporated in Illinois in 1923 and is successor to a number of companies, the oldest of which was organized in 1902. Ameren Illinois supplies electric and natural gas utility service to portions of central and southern Illinois having an estimated population of </font><font style="font-family:Arial Narrow;font-size:10pt;color:#000000;text-decoration:none;">3.1 million</font><font style="font-family:Arial Narrow;font-size:10pt;"> in an area of </font><font style="font-family:Arial Narrow;font-size:10pt;color:#000000;text-decoration:none;">40,000</font><font style="font-family:Arial Narrow;font-size:10pt;"> square miles. Ameren Illinois supplies electric service to </font><font style="font-family:Arial Narrow;font-size:10pt;color:#000000;text-decoration:none;">1.2 million</font><font style="font-family:Arial Narrow;font-size:10pt;"> customers and natural gas service to </font><font style="font-family:Arial Narrow;font-size:10pt;color:#000000;text-decoration:none;">806,000</font><font style="font-family:Arial Narrow;font-size:10pt;"> customers.</font></div></td></tr></table><table cellpadding="0" cellspacing="0" style="font-family:Times New Roman; font-size:10pt;"><tr><td style="width:24px;" rowspan="1" colspan="1"></td><td rowspan="1" colspan="1"></td></tr><tr><td style="vertical-align:top" rowspan="1" colspan="1"><div style="line-height:120%;font-size:10pt;padding-left:0px;"><font style="font-family:Arial Narrow;font-size:10pt;">•</font></div></td><td style="vertical-align:top;" rowspan="1" colspan="1"><div style="line-height:120%;font-size:10pt;"><font style="font-family:Arial Narrow;font-size:10pt;">AER consists of non-rate-regulated operations, including Genco, AERG, Marketing Company, and, through Genco, an </font><font style="font-family:Arial Narrow;font-size:10pt;color:#000000;text-decoration:none;">80%</font><font style="font-family:Arial Narrow;font-size:10pt;"> ownership interest in EEI, which Ameren consolidates for financial reporting purposes.</font></div></td></tr></table><div style="line-height:120%;padding-top:13px;text-indent:24px;font-size:10pt;"><font style="font-family:Arial Narrow;font-size:10pt;">Ameren has various other subsidiaries responsible for activities such as the provision of shared services.</font></div><div style="line-height:120%;padding-top:13px;text-align:left;text-indent:24px;font-size:10pt;"><font style="font-family:Arial Narrow;font-size:10pt;">In December 2012, Ameren determined that it intends to, and it is probable that it will, exit its Merchant Generation business before the end of the previously estimated useful lives of that business's long-lived assets. This determination resulted from Ameren’s analysis of the current and projected future financial condition of its Merchant Generation business segment, including the need to fund Genco debt maturities beginning in 2018, and its conclusion that this business segment is no longer a core component of its future business strategy. In consideration of this determination, Ameren has begun planning to reduce, and ultimately to eliminate, the Merchant Generation business segment’s, including Genco's, reliance on Ameren’s financial support and shared services support. Furthermore, Ameren recorded a noncash long-lived asset impairment charge to reduce the carrying values of the Merchant Generation energy centers, except for the Joppa coal-fired energy center, to their estimated fair values. See Note 17 - Impairment and Other Charges for additional information. Ameren's date and method of exit from the Merchant Generation business is currently uncertain. Exit strategies may include the sale of all or parts of the Merchant Generation business and the restructuring of all or a portion of Ameren's equity position in Genco. Ameren's Merchant Generation long-lived assets have not been classified as held-for-sale under authoritative accounting guidance as all criteria to qualify for that presentation were not met as of December 31, 2012. Specifically, Ameren did not consider it probable that a disposition would occur within one year. </font></div><div style="line-height:120%;padding-top:13px;text-indent:24px;font-size:10pt;"><font style="font-family:Arial Narrow;font-size:10pt;">On October 1, 2010, Ameren, CIPS, CILCO, IP, AERG and AER completed a two-step corporate internal reorganization. The first step of the reorganization was the Ameren Illinois Merger. The second step of the reorganization involved the distribution of AERG stock from Ameren Illinois to Ameren and the subsequent contribution by Ameren of the AERG stock to AER. Ameren Illinois segregated AERG’s operating results and cash flows and presented them separately as discontinued operations in its consolidated statement of income and consolidated statement of cash flows, respectively, for all periods presented prior to October 1, 2010, in this report. See Note 16 - 2010 Corporate Reorganization for additional information.</font></div></div>
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CY2011	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-1120000000	USD
CY2012	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-426000000	USD
CY2011	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-1048000000	USD
CY2012	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	1690000000	USD
CY2011	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	1878000000	USD
CY2010	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	1823000000	USD
CY2010	us-gaap	Net Income Loss NetIncomeLoss	139000000	USD
CY2011	us-gaap	Net Income Loss NetIncomeLoss	519000000	USD
CY2012	us-gaap	Net Income Loss NetIncomeLoss	-974000000	USD
CY2012Q4	us-gaap	Net Income Loss NetIncomeLoss	-1156000000	USD
CY2012Q3	us-gaap	Net Income Loss NetIncomeLoss	374000000	USD
CY2011Q2	us-gaap	Net Income Loss NetIncomeLoss	138000000	USD
CY2011Q1	us-gaap	Net Income Loss NetIncomeLoss	71000000	USD
CY2012Q2	us-gaap	Net Income Loss NetIncomeLoss	211000000	USD
CY2012Q1	us-gaap	Net Income Loss NetIncomeLoss	-403000000	USD
CY2011Q3	us-gaap	Net Income Loss NetIncomeLoss	285000000	USD
CY2011Q4	us-gaap	Net Income Loss NetIncomeLoss	25000000	USD
CY2010	us-gaap	Net Income Loss Attributable To Noncontrolling Interest NetIncomeLossAttributableToNoncontrollingInterest	12000000	USD
CY2012	us-gaap	Net Income Loss Attributable To Noncontrolling Interest NetIncomeLossAttributableToNoncontrollingInterest		USD
CY2011	us-gaap	Net Income Loss Attributable To Noncontrolling Interest NetIncomeLossAttributableToNoncontrollingInterest	7000000	USD
CY2012	us-gaap	Number Of Reportable Segments NumberOfReportableSegments	3	segment
CY2011	us-gaap	Operating Expenses OperatingExpenses	6290000000	USD
CY2012	us-gaap	Operating Expenses OperatingExpenses	8068000000	USD
CY2010	us-gaap	Operating Expenses OperatingExpenses	6722000000	USD
CY2012	us-gaap	Operating Income Loss OperatingIncomeLoss	-1240000000	USD
CY2011	us-gaap	Operating Income Loss OperatingIncomeLoss	1241000000	USD
CY2010	us-gaap	Operating Income Loss OperatingIncomeLoss	916000000	USD
CY2011Q1	us-gaap	Operating Income Loss OperatingIncomeLoss	227000000	USD
CY2012Q1	us-gaap	Operating Income Loss OperatingIncomeLoss	-422000000	USD
CY2011Q3	us-gaap	Operating Income Loss OperatingIncomeLoss	550000000	USD
CY2012Q2	us-gaap	Operating Income Loss OperatingIncomeLoss	363000000	USD
CY2012Q4	us-gaap	Operating Income Loss OperatingIncomeLoss	-1816000000	USD
CY2011Q2	us-gaap	Operating Income Loss OperatingIncomeLoss	316000000	USD
CY2011Q4	us-gaap	Operating Income Loss OperatingIncomeLoss	148000000	USD
CY2012Q3	us-gaap	Operating Income Loss OperatingIncomeLoss	635000000	USD
CY2012Q4	us-gaap	Operating Leases Future Minimum Payments Due OperatingLeasesFutureMinimumPaymentsDue	272000000	USD
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CY2012Q4	us-gaap	Operating Leases Future Minimum Payments Due In Five Years OperatingLeasesFutureMinimumPaymentsDueInFiveYears	25000000	USD
CY2012Q4	us-gaap	Operating Leases Future Minimum Payments Due In Four Years OperatingLeasesFutureMinimumPaymentsDueInFourYears	26000000	USD
CY2012Q4	us-gaap	Operating Leases Future Minimum Payments Due In Three Years OperatingLeasesFutureMinimumPaymentsDueInThreeYears	26000000	USD
CY2012Q4	us-gaap	Operating Leases Future Minimum Payments Due In Two Years OperatingLeasesFutureMinimumPaymentsDueInTwoYears	27000000	USD
CY2012Q4	us-gaap	Operating Leases Future Minimum Payments Due Thereafter OperatingLeasesFutureMinimumPaymentsDueThereafter	137000000	USD
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CY2012Q4	us-gaap	Other Assets Current OtherAssetsCurrent	95000000	USD
CY2012Q4	us-gaap	Other Assets Noncurrent OtherAssetsNoncurrent	749000000	USD
CY2011Q4	us-gaap	Other Assets Noncurrent OtherAssetsNoncurrent	845000000	USD
CY2010	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-6000000	USD
CY2012	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	50000000	USD
CY2011	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-39000000	USD
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CY2011	us-gaap	Other Income OtherIncome	3000000	USD
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CY2012	us-gaap	Other Interest And Dividend Income OtherInterestAndDividendIncome	5000000	USD
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CY2012Q4	us-gaap	Other Liabilities Current OtherLiabilitiesCurrent	188000000	USD
CY2012Q4	us-gaap	Other Liabilities Noncurrent OtherLiabilitiesNoncurrent	668000000	USD
CY2011Q4	us-gaap	Other Liabilities Noncurrent OtherLiabilitiesNoncurrent	447000000	USD
CY2012	us-gaap	Other Noncash Income Expense OtherNoncashIncomeExpense	-25000000	USD
CY2010	us-gaap	Other Noncash Income Expense OtherNoncashIncomeExpense	-21000000	USD
CY2011	us-gaap	Other Noncash Income Expense OtherNoncashIncomeExpense		USD
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CY2011	us-gaap	Other Noninterest Expense OtherNoninterestExpense	15000000	USD
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CY2010	us-gaap	Other Nonoperating Expense OtherNonoperatingExpense	33000000	USD
CY2011	us-gaap	Other Nonoperating Expense OtherNonoperatingExpense	23000000	USD
CY2010	us-gaap	Other Nonoperating Income OtherNonoperatingIncome	90000000	USD
CY2011	us-gaap	Other Nonoperating Income OtherNonoperatingIncome	69000000	USD
CY2012	us-gaap	Other Nonoperating Income OtherNonoperatingIncome	71000000	USD
CY2010	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	57000000	USD
CY2012	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	34000000	USD
CY2011	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	46000000	USD
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CY2012Q4	us-gaap	Other Receivables Net Current OtherReceivablesNetCurrent	95000000	USD
CY2011	us-gaap	Payment Of Financing And Stock Issuance Costs PaymentOfFinancingAndStockIssuanceCosts		USD
CY2010	us-gaap	Payment Of Financing And Stock Issuance Costs PaymentOfFinancingAndStockIssuanceCosts	15000000	USD
CY2012	us-gaap	Payment Of Financing And Stock Issuance Costs PaymentOfFinancingAndStockIssuanceCosts	16000000	USD
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CY2011	us-gaap	Payments For Nuclear Fuel PaymentsForNuclearFuel	62000000	USD
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CY2011	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	-12000000	USD
CY2010	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	-2000000	USD
CY2011	us-gaap	Payments For Repurchase Of Preferred Stock And Preference Stock PaymentsForRepurchaseOfPreferredStockAndPreferenceStock		USD
CY2012	us-gaap	Payments For Repurchase Of Preferred Stock And Preference Stock PaymentsForRepurchaseOfPreferredStockAndPreferenceStock		USD
CY2010	us-gaap	Payments For Repurchase Of Preferred Stock And Preference Stock PaymentsForRepurchaseOfPreferredStockAndPreferenceStock	52000000	USD
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CY2012	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	382000000	USD
CY2010	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	368000000	USD
CY2012	us-gaap	Payments Of Dividends Minority Interest PaymentsOfDividendsMinorityInterest	6000000	USD
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CY2010	us-gaap	Payments Of Dividends Minority Interest PaymentsOfDividendsMinorityInterest	8000000	USD
CY2010	us-gaap	Payments To Acquire Other Investments PaymentsToAcquireOtherInvestments	271000000	USD
CY2011	us-gaap	Payments To Acquire Other Investments PaymentsToAcquireOtherInvestments	220000000	USD
CY2012	us-gaap	Payments To Acquire Other Investments PaymentsToAcquireOtherInvestments	403000000	USD
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CY2011Q4	us-gaap	Pension And Other Postretirement Defined Benefit Plans Liabilities Noncurrent PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent	1344000000	USD
CY2012Q4	us-gaap	Preferred Stock Liquidation Preference PreferredStockLiquidationPreference	105.50
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CY2012Q4	us-gaap	Preferred Stock Value PreferredStockValue	142000000	USD
CY2011	us-gaap	Proceeds From Advances For Construction ProceedsFromAdvancesForConstruction	5000000	USD
CY2012	us-gaap	Proceeds From Advances For Construction ProceedsFromAdvancesForConstruction	4000000	USD
CY2010	us-gaap	Proceeds From Advances For Construction ProceedsFromAdvancesForConstruction	29000000	USD
CY2011	us-gaap	Proceeds From Issuance Of Common Stock ProceedsFromIssuanceOfCommonStock	65000000	USD
CY2012	us-gaap	Proceeds From Issuance Of Common Stock ProceedsFromIssuanceOfCommonStock		USD
CY2010	us-gaap	Proceeds From Issuance Of Common Stock ProceedsFromIssuanceOfCommonStock	80000000	USD
CY2011	us-gaap	Proceeds From Issuance Of Long Term Debt ProceedsFromIssuanceOfLongTermDebt		USD
CY2012	us-gaap	Proceeds From Issuance Of Long Term Debt ProceedsFromIssuanceOfLongTermDebt	882000000	USD
CY2010	us-gaap	Proceeds From Issuance Of Long Term Debt ProceedsFromIssuanceOfLongTermDebt		USD
CY2012	us-gaap	Proceeds From Repayments Of Short Term Debt ProceedsFromRepaymentsOfShortTermDebt	-148000000	USD
CY2010	us-gaap	Proceeds From Repayments Of Short Term Debt ProceedsFromRepaymentsOfShortTermDebt	-121000000	USD
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CY2010	us-gaap	Proceeds From Sale And Maturity Of Other Investments ProceedsFromSaleAndMaturityOfOtherInvestments	256000000	USD
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CY2011	us-gaap	Proceeds From Sale And Maturity Of Other Investments ProceedsFromSaleAndMaturityOfOtherInvestments	199000000	USD
CY2011	us-gaap	Proceeds From Sale Of Property Plant And Equipment ProceedsFromSaleOfPropertyPlantAndEquipment	53000000	USD
CY2012	us-gaap	Proceeds From Sale Of Property Plant And Equipment ProceedsFromSaleOfPropertyPlantAndEquipment	22000000	USD
CY2010	us-gaap	Proceeds From Sale Of Property Plant And Equipment ProceedsFromSaleOfPropertyPlantAndEquipment	27000000	USD
CY2011	us-gaap	Profit Loss ProfitLoss	526000000	USD
CY2010	us-gaap	Profit Loss ProfitLoss	151000000	USD
CY2012	us-gaap	Profit Loss ProfitLoss	-974000000	USD
CY2012Q4	us-gaap	Property Plant And Equipment Gross PropertyPlantAndEquipmentGross	23909000000	USD
CY2011Q4	us-gaap	Property Plant And Equipment Gross PropertyPlantAndEquipmentGross	26468000000	USD
CY2011Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	18127000000	USD
CY2012Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	16096000000	USD
CY2010	us-gaap	Public Utilities Allowance For Funds Used During Construction Capitalized Cost Of Equity PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedCostOfEquity	52000000	USD
CY2011	us-gaap	Public Utilities Allowance For Funds Used During Construction Capitalized Cost Of Equity PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedCostOfEquity	34000000	USD
CY2012	us-gaap	Public Utilities Allowance For Funds Used During Construction Capitalized Cost Of Equity PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedCostOfEquity	36000000	USD
CY2012Q1	us-gaap	Revenues Revenues	1658000000	USD
CY2012Q2	us-gaap	Revenues Revenues	1660000000	USD
CY2011Q4	us-gaap	Public Utilities Inventory PublicUtilitiesInventory	290000000	USD
CY2012Q4	us-gaap	Public Utilities Inventory PublicUtilitiesInventory	297000000	USD
CY2011Q4	us-gaap	Regulated Entity Other Assets Noncurrent RegulatedEntityOtherAssetsNoncurrent	3223000000	USD
CY2012Q4	us-gaap	Regulated Entity Other Assets Noncurrent RegulatedEntityOtherAssetsNoncurrent	3370000000	USD
CY2012Q4	us-gaap	Regulatory Assets Current RegulatoryAssetsCurrent	247000000	USD
CY2011Q4	us-gaap	Regulatory Assets Current RegulatoryAssetsCurrent	215000000	USD
CY2012Q4	us-gaap	Regulatory Assets Noncurrent RegulatoryAssetsNoncurrent	1786000000	USD
CY2011Q4	us-gaap	Regulatory Assets Noncurrent RegulatoryAssetsNoncurrent	1603000000	USD
CY2012Q4	us-gaap	Regulatory Liability Current RegulatoryLiabilityCurrent	100000000	USD
CY2011Q4	us-gaap	Regulatory Liability Current RegulatoryLiabilityCurrent	133000000	USD
CY2012Q4	us-gaap	Regulatory Liability Noncurrent RegulatoryLiabilityNoncurrent	1589000000	USD
CY2011Q4	us-gaap	Regulatory Liability Noncurrent RegulatoryLiabilityNoncurrent	1502000000	USD
CY2012	us-gaap	Repayments Of Other Long Term Debt RepaymentsOfOtherLongTermDebt	760000000	USD
CY2010	us-gaap	Repayments Of Other Long Term Debt RepaymentsOfOtherLongTermDebt	310000000	USD
CY2011	us-gaap	Repayments Of Other Long Term Debt RepaymentsOfOtherLongTermDebt	155000000	USD
CY2012Q4	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	1006000000	USD
CY2011Q4	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	2369000000	USD
CY2011	us-gaap	Revenues Revenues	7531000000	USD
CY2012	us-gaap	Revenues Revenues	6828000000	USD
CY2010	us-gaap	Revenues Revenues	7638000000	USD
CY2011Q4	us-gaap	Revenues Revenues	1578000000	USD
CY2011Q1	us-gaap	Revenues Revenues	1904000000	USD
CY2012Q4	us-gaap	Revenues Revenues	1509000000	USD
CY2011Q2	us-gaap	Revenues Revenues	1781000000	USD
CY2011Q3	us-gaap	Revenues Revenues	2268000000	USD
CY2012Q3	us-gaap	Revenues Revenues	2001000000	USD
CY2010	us-gaap	Taxes Excluding Income And Excise Taxes TaxesExcludingIncomeAndExciseTaxes	449000000	USD
CY2011	us-gaap	Taxes Excluding Income And Excise Taxes TaxesExcludingIncomeAndExciseTaxes	457000000	USD
CY2011Q4	us-gaap	Taxes Payable Current TaxesPayableCurrent	65000000	USD
CY2012Q4	us-gaap	Taxes Payable Current TaxesPayableCurrent	68000000	USD
CY2012Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Number Of Shares Available For Grant ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant	4000000	shares
CY2011Q4	us-gaap	Short Term Borrowings ShortTermBorrowings	148000000	USD
CY2012Q4	us-gaap	Short Term Borrowings ShortTermBorrowings		USD
CY2012	us-gaap	Stock Issued During Period Shares New Issues StockIssuedDuringPeriodSharesNewIssues		shares
CY2011	us-gaap	Stock Issued During Period Shares New Issues StockIssuedDuringPeriodSharesNewIssues	2200000	shares
CY2010	us-gaap	Stock Issued During Period Shares New Issues StockIssuedDuringPeriodSharesNewIssues	3000000	shares
CY2012Q4	us-gaap	Stockholders Equity StockholdersEquity	6616000000	USD
CY2011Q4	us-gaap	Stockholders Equity StockholdersEquity	7919000000	USD
CY2011Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	8068000000	USD
CY2012Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	6767000000	USD
CY2010Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	7884000000	USD
CY2012Q4	us-gaap	Tax Credit Carryforward Amount TaxCreditCarryforwardAmount	118000000	USD
CY2012	us-gaap	Taxes Excluding Income And Excise Taxes TaxesExcludingIncomeAndExciseTaxes	468000000	USD
CY2010	aee	Annual Decommissioning Costs Included In Costs Of Service AnnualDecommissioningCostsIncludedInCostsOfService	7000000	USD
CY2012Q4	aee	Annual Obligation For Real Estate Leases And Railroad Licenses AnnualObligationForRealEstateLeasesAndRailroadLicenses	2000000	USD
CY2011Q4	us-gaap	Unbilled Receivables Current UnbilledReceivablesCurrent	324000000	USD
CY2012Q4	us-gaap	Unbilled Receivables Current UnbilledReceivablesCurrent	322000000	USD
CY2011	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	241500000	shares
CY2012Q4	aee	Accumulated Depreciation Capital Lease AccumulatedDepreciationCapitalLease	52000000	USD
CY2011Q4	aee	Accumulated Depreciation Capital Lease AccumulatedDepreciationCapitalLease	52000000	USD
CY2012	aee	Actual Return In Excess Of Or Less Than Expected Return Percentage ActualReturnInExcessOfOrLessThanExpectedReturnPercentage	0.25
CY2012	aee	Aggregate Maximum Assessment Per Incident Under Price Andersen Liability Provisions Of Atomic Energy Act AggregateMaximumAssessmentPerIncidentUnderPriceAndersenLiabilityProvisionsOfAtomicEnergyAct	118000000	USD
CY2012	aee	Aggregate Nuclear Power Industry Insurance Policy Limit For Losses From Terrorist Attacks Within Twelve Month Period AggregateNuclearPowerIndustryInsurancePolicyLimitForLossesFromTerroristAttacksWithinTwelveMonthPeriod	3240000000	USD
CY2012	aee	Amount Gain Loss On Derivative Instruments That Qualify For Regulatory Deferral Net AmountGainLossOnDerivativeInstrumentsThatQualifyForRegulatoryDeferralNet	-112000000	USD
CY2011	aee	Amount Gain Loss On Derivative Instruments That Qualify For Regulatory Deferral Net AmountGainLossOnDerivativeInstrumentsThatQualifyForRegulatoryDeferralNet	51000000	USD
CY2012	us-gaap	Unrealized Gain Loss On Derivatives UnrealizedGainLossOnDerivatives	-22000000	USD
CY2011	us-gaap	Unrealized Gain Loss On Derivatives UnrealizedGainLossOnDerivatives	-11000000	USD
CY2010	us-gaap	Unrealized Gain Loss On Derivatives UnrealizedGainLossOnDerivatives	15000000	USD
CY2009Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	135000000	USD
CY2011Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	148000000	USD
CY2012Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	156000000	USD
CY2010Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	246000000	USD
CY2012	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions	13000000	USD
CY2010	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions	38000000	USD
CY2011	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions	125000000	USD
CY2012	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Settlements With Taxing Authorities UnrecognizedTaxBenefitsDecreasesResultingFromSettlementsWithTaxingAuthorities		USD
CY2011	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Settlements With Taxing Authorities UnrecognizedTaxBenefitsDecreasesResultingFromSettlementsWithTaxingAuthorities	10000000	USD
CY2010	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Settlements With Taxing Authorities UnrecognizedTaxBenefitsDecreasesResultingFromSettlementsWithTaxingAuthorities		USD
CY2011	us-gaap	Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions	17000000	USD
CY2010	us-gaap	Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions	77000000	USD
CY2012	us-gaap	Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions	17000000	USD
CY2011	us-gaap	Unrecognized Tax Benefits Increases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions	22000000	USD
CY2010	us-gaap	Unrecognized Tax Benefits Increases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions	72000000	USD
CY2012	us-gaap	Unrecognized Tax Benefits Increases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions	5000000	USD
CY2010Q4	us-gaap	Unrecognized Tax Benefits Interest On Income Taxes Accrued UnrecognizedTaxBenefitsInterestOnIncomeTaxesAccrued	17000000	USD
CY2009Q4	us-gaap	Unrecognized Tax Benefits Interest On Income Taxes Accrued UnrecognizedTaxBenefitsInterestOnIncomeTaxesAccrued	8000000	USD
CY2012Q4	us-gaap	Unrecognized Tax Benefits Interest On Income Taxes Accrued UnrecognizedTaxBenefitsInterestOnIncomeTaxesAccrued	6000000	USD
CY2011Q4	us-gaap	Unrecognized Tax Benefits Interest On Income Taxes Accrued UnrecognizedTaxBenefitsInterestOnIncomeTaxesAccrued	5000000	USD
CY2010	us-gaap	Unrecognized Tax Benefits Interest On Income Taxes Expense UnrecognizedTaxBenefitsInterestOnIncomeTaxesExpense	-9000000	USD
CY2011	us-gaap	Unrecognized Tax Benefits Interest On Income Taxes Expense UnrecognizedTaxBenefitsInterestOnIncomeTaxesExpense	11000000	USD
CY2012	us-gaap	Unrecognized Tax Benefits Interest On Income Taxes Expense UnrecognizedTaxBenefitsInterestOnIncomeTaxesExpense	-1000000	USD
CY2010	us-gaap	Unrecognized Tax Benefits Reductions Resulting From Lapse Of Applicable Statute Of Limitations UnrecognizedTaxBenefitsReductionsResultingFromLapseOfApplicableStatuteOfLimitations		USD
CY2011	us-gaap	Unrecognized Tax Benefits Reductions Resulting From Lapse Of Applicable Statute Of Limitations UnrecognizedTaxBenefitsReductionsResultingFromLapseOfApplicableStatuteOfLimitations	2000000	USD
CY2012	us-gaap	Unrecognized Tax Benefits Reductions Resulting From Lapse Of Applicable Statute Of Limitations UnrecognizedTaxBenefitsReductionsResultingFromLapseOfApplicableStatuteOfLimitations	1000000	USD
CY2010Q4	us-gaap	Unrecognized Tax Benefits That Would Impact Effective Tax Rate UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate		USD
CY2011Q4	us-gaap	Unrecognized Tax Benefits That Would Impact Effective Tax Rate UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate	1000000	USD
CY2012Q4	us-gaap	Unrecognized Tax Benefits That Would Impact Effective Tax Rate UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate	1000000	USD
CY2012Q4	us-gaap	Unrecorded Unconditional Purchase Obligation Balance On Fifth Anniversary UnrecordedUnconditionalPurchaseObligationBalanceOnFifthAnniversary	923000000	USD
CY2012Q4	us-gaap	Unrecorded Unconditional Purchase Obligation Balance On First Anniversary UnrecordedUnconditionalPurchaseObligationBalanceOnFirstAnniversary	1891000000	USD
CY2012Q4	us-gaap	Unrecorded Unconditional Purchase Obligation Balance On Fourth Anniversary UnrecordedUnconditionalPurchaseObligationBalanceOnFourthAnniversary	1025000000	USD
CY2012Q4	us-gaap	Unrecorded Unconditional Purchase Obligation Balance On Second Anniversary UnrecordedUnconditionalPurchaseObligationBalanceOnSecondAnniversary	1596000000	USD
CY2012Q4	us-gaap	Unrecorded Unconditional Purchase Obligation Balance On Third Anniversary UnrecordedUnconditionalPurchaseObligationBalanceOnThirdAnniversary	1212000000	USD
CY2012Q4	us-gaap	Unrecorded Unconditional Purchase Obligation Balance Sheet Amount UnrecordedUnconditionalPurchaseObligationBalanceSheetAmount	8338000000	USD
CY2012Q4	us-gaap	Unrecorded Unconditional Purchase Obligation Due After Five Years UnrecordedUnconditionalPurchaseObligationDueAfterFiveYears	1691000000	USD
CY2011	us-gaap	Utilities Operating Expense Maintenance Operations And Other Costs And Expenses UtilitiesOperatingExpenseMaintenanceOperationsAndOtherCostsAndExpenses	1820000000	USD
CY2012	us-gaap	Utilities Operating Expense Maintenance Operations And Other Costs And Expenses UtilitiesOperatingExpenseMaintenanceOperationsAndOtherCostsAndExpenses	1752000000	USD
CY2010	us-gaap	Utilities Operating Expense Maintenance Operations And Other Costs And Expenses UtilitiesOperatingExpenseMaintenanceOperationsAndOtherCostsAndExpenses	1821000000	USD
CY2010	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	238800000	shares
CY2012	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	242600000	shares
CY2012	aee	Amount Of Additional Weekly Indemnity Coverage Commencing After Initial Indemnity Coverage AmountOfAdditionalWeeklyIndemnityCoverageCommencingAfterInitialIndemnityCoverage	3600000	USD
CY2012	aee	Amount Of Coverage In Excess Of Primary Property Liability Coverage AmountOfCoverageInExcessOfPrimaryPropertyLiabilityCoverage	2250000000	USD
CY2012	aee	Amount Of Primary Property Liability Coverage AmountOfPrimaryPropertyLiabilityCoverage	500000000	USD
CY2012	aee	Amount Of Secondary Weekly Indemnity Coverage For Prolonged Nuclear Plant Outage In Excess Of Primary Indemnity Coverage AmountOfSecondaryWeeklyIndemnityCoverageForProlongedNuclearPlantOutageInExcessOfPrimaryIndemnityCoverage	900000	USD
CY2012	aee	Amount Of Weekly Indemnity Coverage Commencing Eight Weeks After Power Outage AmountOfWeeklyIndemnityCoverageCommencingEightWeeksAfterPowerOutage	4500000	USD
CY2012	aee	Amount Of Weekly Indemnity Coverage Thereafter Not Exceeding Policy Limit AmountOfWeeklyIndemnityCoverageThereafterNotExceedingPolicyLimit	490000000	USD
CY2012	aee	Annual Decommissioning Costs Included In Costs Of Service AnnualDecommissioningCostsIncludedInCostsOfService	7000000	USD
CY2011	aee	Annual Decommissioning Costs Included In Costs Of Service AnnualDecommissioningCostsIncludedInCostsOfService	7000000	USD
CY2012Q4	aee	Capital And Operating Lease Obligations Due CapitalAndOperatingLeaseObligationsDue	576000000	USD
CY2012Q4	aee	Capital And Operating Lease Obligations Due Current CapitalAndOperatingLeaseObligationsDueCurrent	36000000	USD
CY2012Q4	aee	Capital And Operating Lease Obligations Due In Year Four CapitalAndOperatingLeaseObligationsDueInYearFour	31000000	USD
CY2012Q4	aee	Capital And Operating Lease Obligations Due In Year One CapitalAndOperatingLeaseObligationsDueInYearOne	32000000	USD
CY2012Q4	aee	Capital And Operating Lease Obligations Due In Year Three CapitalAndOperatingLeaseObligationsDueInYearThree	32000000	USD
CY2012Q4	aee	Capital And Operating Lease Obligations Due In Year Two CapitalAndOperatingLeaseObligationsDueInYearTwo	32000000	USD
CY2012Q4	aee	Capital And Operating Lease Obligations Due Thereafter CapitalAndOperatingLeaseObligationsDueThereafter	413000000	USD
CY2012Q4	aee	Capital Leases Future Minimum Payments Interest Included In Payments Current CapitalLeasesFutureMinimumPaymentsInterestIncludedInPaymentsCurrent	27000000	USD
CY2012Q4	aee	Capital Leases Future Minimum Payments Interest Included In Payments Due In Five Years CapitalLeasesFutureMinimumPaymentsInterestIncludedInPaymentsDueInFiveYears	27000000	USD
CY2012Q4	aee	Capital Leases Future Minimum Payments Interest Included In Payments Due In Four Years CapitalLeasesFutureMinimumPaymentsInterestIncludedInPaymentsDueInFourYears	27000000	USD
CY2012Q4	aee	Capital Leases Future Minimum Payments Interest Included In Payments Due In Three Years CapitalLeasesFutureMinimumPaymentsInterestIncludedInPaymentsDueInThreeYears	27000000	USD
CY2012Q4	aee	Capital Leases Future Minimum Payments Interest Included In Payments Due In Two Years CapitalLeasesFutureMinimumPaymentsInterestIncludedInPaymentsDueInTwoYears	27000000	USD
CY2012Q4	aee	Capital Leases Future Minimum Payments Interest Included In Payments Thereafter CapitalLeasesFutureMinimumPaymentsInterestIncludedInPaymentsThereafter	149000000	USD
CY2012Q4	aee	Capital Leases Future Minimum Payments Present Value Of Net Minimum Payments Current CapitalLeasesFutureMinimumPaymentsPresentValueOfNetMinimumPaymentsCurrent	5000000	USD
CY2012Q4	aee	Capital Leases Future Minimum Payments Present Value Of Net Minimum Payments Due In Five Years CapitalLeasesFutureMinimumPaymentsPresentValueOfNetMinimumPaymentsDueInFiveYears	6000000	USD
CY2012Q4	aee	Capital Leases Future Minimum Payments Present Value Of Net Minimum Payments Due In Four Years CapitalLeasesFutureMinimumPaymentsPresentValueOfNetMinimumPaymentsDueInFourYears	6000000	USD
CY2012Q4	aee	Capital Leases Future Minimum Payments Present Value Of Net Minimum Payments Due In Three Years CapitalLeasesFutureMinimumPaymentsPresentValueOfNetMinimumPaymentsDueInThreeYears	6000000	USD
CY2012Q4	aee	Capital Leases Future Minimum Payments Present Value Of Net Minimum Payments Due In Two Years CapitalLeasesFutureMinimumPaymentsPresentValueOfNetMinimumPaymentsDueInTwoYears	5000000	USD
CY2012Q4	aee	Capital Leases Future Minimum Payments Present Value Of Net Minimum Payments Thereafter CapitalLeasesFutureMinimumPaymentsPresentValueOfNetMinimumPaymentsThereafter	276000000	USD
CY2012	aee	Debt Default Provision Excess DebtDefaultProvisionExcess	25000000	USD
CY2012Q4	aee	Deferred Tax Liabilities Intercompany Tax Gain Basis Step Up DeferredTaxLiabilitiesIntercompanyTaxGainBasisStepUp	2000000	USD
CY2011Q4	aee	Deferred Tax Liabilities Intercompany Tax Gain Basis Step Up DeferredTaxLiabilitiesIntercompanyTaxGainBasisStepUp	3000000	USD
CY2012Q4	aee	Defined Benefit Plan Estimated Future Employer Contributions Over Next Five Years DefinedBenefitPlanEstimatedFutureEmployerContributionsOverNextFiveYears	550000000	USD
CY2012	aee	Defined Benefit Plan Expected Return On Plan Assets Period DefinedBenefitPlanExpectedReturnOnPlanAssetsPeriod	P4Y
CY2012	aee	Defined Benefit Plan Future Amortization Of Prior Service Cost Credit Period DefinedBenefitPlanFutureAmortizationOfPriorServiceCostCreditPeriod	P10Y
CY2012	aee	Defined Benefit Plan Number Of High Quality Bonds Used To Determine Yield Curve DefinedBenefitPlanNumberOfHighQualityBondsUsedToDetermineYieldCurve	600	bond
CY2012Q4	aee	Department Of Energy Investing Funding Support Number Of Small Modular Reactor Designs DepartmentOfEnergyInvestingFundingSupportNumberOfSmallModularReactorDesigns	2
CY2012Q4	aee	Department Of Energy Investing Funding Support Number Of Small Modular Reactor Designs Awarded DepartmentOfEnergyInvestingFundingSupportNumberOfSmallModularReactorDesignsAwarded	1
CY2012	aee	Department Of Energy Investing Funding Support Period DepartmentOfEnergyInvestingFundingSupportPeriod	P5Y
CY2011Q4	aee	Derivative Liabilities Current Carrying Amount DerivativeLiabilitiesCurrentCarryingAmount	161000000	USD
CY2012Q4	aee	Derivative Liabilities Current Carrying Amount DerivativeLiabilitiesCurrentCarryingAmount	155000000	USD
CY2011Q4	aee	Derivative Potential Loss DerivativePotentialLoss	750000000	USD
CY2012Q4	aee	Derivative Potential Loss DerivativePotentialLoss	398000000	USD
CY2012	aee	Disclosure Of Accrued Capital Expenditures Excluded From Statements Of Cash Flow DisclosureOfAccruedCapitalExpendituresExcludedFromStatementsOfCashFlow	<div style="font-family:Times New Roman;font-size:10pt;"><div style="line-height:120%;padding-left:4px;padding-top:13px;text-align:left;text-indent:24px;font-size:10pt;"><font style="font-family:Arial Narrow;font-size:10pt;">The following table provides accrued capital expenditures at </font><font style="font-family:Arial Narrow;font-size:10pt;color:#000000;text-decoration:none;">December 31, 2012</font><font style="font-family:Arial Narrow;font-size:10pt;">, </font><font style="font-family:Arial Narrow;font-size:10pt;color:#000000;text-decoration:none;">2011</font><font style="font-family:Arial Narrow;font-size:10pt;">, and </font><font style="font-family:Arial Narrow;font-size:10pt;color:#000000;text-decoration:none;">2010</font><font style="font-family:Arial Narrow;font-size:10pt;">, which represent noncash investing activity excluded from the statements of cash flows:</font></div><div style="line-height:100%;font-size:10pt;"><div style="padding-left:0px;text-indent:0px;line-height:normal;padding-top:10px;"><table cellpadding="0" cellspacing="0" style="font-family:Times New Roman;font-size:10pt;width:93.0672268907563%;border-collapse:collapse;text-align:left;"><tr><td colspan="12" rowspan="1"></td></tr><tr><td width="53%" rowspan="1" colspan="1"></td><td width="1%" rowspan="1" colspan="1"></td><td width="13%" rowspan="1" colspan="1"></td><td width="1%" rowspan="1" colspan="1"></td><td width="1%" rowspan="1" colspan="1"></td><td width="1%" rowspan="1" colspan="1"></td><td width="13%" rowspan="1" colspan="1"></td><td width="1%" rowspan="1" colspan="1"></td><td width="1%" rowspan="1" colspan="1"></td><td width="1%" rowspan="1" colspan="1"></td><td width="13%" rowspan="1" colspan="1"></td><td width="1%" rowspan="1" colspan="1"></td></tr><tr><td style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;border-top:2px solid #000000;" rowspan="1" colspan="1"><div style="overflow:hidden;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;"> </font></div></td><td colspan="3" style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;border-top:2px solid #000000;" rowspan="1"><div style="font-family:Arial Narrow;text-align:center;font-size:10pt;"><font style="font-family:Arial Narrow;font-size:8pt;font-weight:bold;">Ameren</font><font style="font-family:Arial Narrow;font-size:10pt;font-weight:bold;"><sup style="vertical-align:top;line-height:120%;font-size:6pt">(a)</sup></font></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;border-top:2px solid #000000;" rowspan="1" colspan="1"><div style="overflow:hidden;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;"> </font></div></td><td colspan="3" style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;border-top:2px solid #000000;" rowspan="1"><div style="font-family:Arial Narrow;text-align:center;font-size:8pt;"><font style="font-family:Arial Narrow;font-size:8pt;font-weight:bold;">Ameren</font></div><div style="font-family:Arial Narrow;text-align:center;font-size:8pt;"><font style="font-family:Arial Narrow;font-size:8pt;font-weight:bold;">Missouri</font></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;border-top:2px solid #000000;" rowspan="1" colspan="1"><div style="overflow:hidden;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;"> </font></div></td><td colspan="3" style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;border-top:2px solid #000000;" rowspan="1"><div style="font-family:Arial Narrow;text-align:center;font-size:8pt;"><font style="font-family:Arial Narrow;font-size:8pt;font-weight:bold;">Ameren</font></div><div style="font-family:Arial Narrow;text-align:center;font-size:8pt;"><font style="font-family:Arial Narrow;font-size:8pt;font-weight:bold;">Illinois</font></div></td></tr><tr><td style="vertical-align:top;background-color:#cceeff;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;border-top:1px solid #000000;" rowspan="1" colspan="1"><div style="text-align:left;font-size:8pt;"><font style="font-family:Arial Narrow;font-size:8pt;">2012</font></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;background-color:#cceeff;" rowspan="1" colspan="1"><div style="text-align:left;font-size:8pt;"><font style="font-family:Arial Narrow;font-size:8pt;font-weight:bold;">$</font></div></td><td style="vertical-align:bottom;background-color:#cceeff;padding-top:2px;padding-bottom:2px;" rowspan="1" colspan="1"><div style="text-align:right;font-size:8pt;"><font style="font-family:Arial Narrow;font-size:8pt;font-weight:bold;">108</font></div></td><td style="vertical-align:bottom;background-color:#cceeff;" rowspan="1" colspan="1"><div style="text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;"><br clear="none"/></font></div></td><td style="vertical-align:bottom;background-color:#cceeff;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="overflow:hidden;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;"> </font></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;background-color:#cceeff;" rowspan="1" colspan="1"><div style="text-align:left;font-size:8pt;"><font style="font-family:Arial Narrow;font-size:8pt;font-weight:bold;">$</font></div></td><td style="vertical-align:bottom;background-color:#cceeff;padding-top:2px;padding-bottom:2px;" rowspan="1" colspan="1"><div style="text-align:right;font-size:8pt;"><font style="font-family:Arial Narrow;font-size:8pt;font-weight:bold;">63</font></div></td><td style="vertical-align:bottom;background-color:#cceeff;" rowspan="1" colspan="1"><div style="text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;"><br clear="none"/></font></div></td><td style="vertical-align:bottom;background-color:#cceeff;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="overflow:hidden;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;"> </font></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;background-color:#cceeff;" rowspan="1" colspan="1"><div style="text-align:left;font-size:8pt;"><font style="font-family:Arial Narrow;font-size:8pt;font-weight:bold;">$</font></div></td><td style="vertical-align:bottom;background-color:#cceeff;padding-top:2px;padding-bottom:2px;" rowspan="1" colspan="1"><div style="text-align:right;font-size:8pt;"><font style="font-family:Arial Narrow;font-size:8pt;font-weight:bold;">37</font></div></td><td style="vertical-align:bottom;background-color:#cceeff;" rowspan="1" colspan="1"><div style="text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;"><br clear="none"/></font></div></td></tr><tr><td style="vertical-align:top;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="text-align:left;font-size:8pt;"><font style="font-family:Arial Narrow;font-size:8pt;">2011</font></div></td><td colspan="2" style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;" rowspan="1"><div style="text-align:right;font-size:8pt;"><font style="font-family:Arial Narrow;font-size:8pt;">107</font></div></td><td style="vertical-align:bottom;" rowspan="1" colspan="1"><div style="text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;"><br clear="none"/></font></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="overflow:hidden;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;"> </font></div></td><td colspan="2" style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;" rowspan="1"><div style="text-align:right;font-size:8pt;"><font style="font-family:Arial Narrow;font-size:8pt;">73</font></div></td><td style="vertical-align:bottom;" rowspan="1" colspan="1"><div style="text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;"><br clear="none"/></font></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="overflow:hidden;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;"> </font></div></td><td colspan="2" style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;" rowspan="1"><div style="text-align:right;font-size:8pt;"><font style="font-family:Arial Narrow;font-size:8pt;">18</font></div></td><td style="vertical-align:bottom;" rowspan="1" colspan="1"><div style="text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;"><br clear="none"/></font></div></td></tr><tr><td style="vertical-align:top;border-bottom:2px solid #000000;background-color:#cceeff;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="text-align:left;font-size:8pt;"><font style="font-family:Arial Narrow;font-size:8pt;">2010</font></div></td><td colspan="2" style="vertical-align:bottom;border-bottom:2px solid #000000;background-color:#cceeff;padding-left:2px;padding-top:2px;padding-bottom:2px;" rowspan="1"><div style="text-align:right;font-size:8pt;"><font style="font-family:Arial Narrow;font-size:8pt;">79</font></div></td><td style="vertical-align:bottom;border-bottom:2px solid #000000;background-color:#cceeff;" rowspan="1" colspan="1"><div style="text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;"><br clear="none"/></font></div></td><td style="vertical-align:bottom;border-bottom:2px solid #000000;background-color:#cceeff;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="overflow:hidden;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;"> </font></div></td><td colspan="2" style="vertical-align:bottom;border-bottom:2px solid #000000;background-color:#cceeff;padding-left:2px;padding-top:2px;padding-bottom:2px;" rowspan="1"><div style="text-align:right;font-size:8pt;"><font style="font-family:Arial Narrow;font-size:8pt;">53</font></div></td><td style="vertical-align:bottom;border-bottom:2px solid #000000;background-color:#cceeff;" rowspan="1" colspan="1"><div style="text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;"><br clear="none"/></font></div></td><td style="vertical-align:bottom;border-bottom:2px solid #000000;background-color:#cceeff;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="overflow:hidden;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;"> </font></div></td><td colspan="2" style="vertical-align:bottom;border-bottom:2px solid #000000;background-color:#cceeff;padding-left:2px;padding-top:2px;padding-bottom:2px;" rowspan="1"><div style="text-align:right;font-size:8pt;"><font style="font-family:Arial Narrow;font-size:8pt;">15</font></div></td><td style="vertical-align:bottom;border-bottom:2px solid #000000;background-color:#cceeff;" rowspan="1" colspan="1"><div style="text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;"><br clear="none"/></font></div></td></tr></table></div><font style="font-family:inherit;font-size:10pt;"><br clear="none"/></font></div><table cellpadding="0" cellspacing="0" style="padding-top:5px;font-family:Times New Roman; font-size:10pt;"><tr><td style="width:24px;" rowspan="1" colspan="1"></td><td rowspan="1" colspan="1"></td></tr><tr><td style="vertical-align:top" rowspan="1" colspan="1"><div style="line-height:120%;font-size:8pt;padding-left:0px;"><font style="font-family:Arial Narrow;font-size:8pt;">(a)</font></div></td><td style="vertical-align:top;" rowspan="1" colspan="1"><div style="line-height:120%;text-align:left;font-size:8pt;"><font style="font-family:Arial Narrow;font-size:8pt;">Includes amounts for Ameren registrant and nonregistrant subsidiaries.</font></div></td></tr></table></div>
CY2012	aee	Donations Donations	24000000	USD
CY2010	aee	Donations Donations	19000000	USD
CY2012Q2	dei	Entity Public Float EntityPublicFloat	8137966865	USD
CY2012	dei	Entity Registrant Name EntityRegistrantName	AMEREN CORP
CY2011	aee	Donations Donations	8000000	USD
CY2013	aee	Estimated Unrecognized Tax Benefits Decreases Resulting From Settlements With Taxing Authorities EstimatedUnrecognizedTaxBenefitsDecreasesResultingFromSettlementsWithTaxingAuthorities	143000000	USD
CY2012	aee	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Transfers Net FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetLiabilityTransfersNet	183000000	USD
CY2011	aee	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Transfers Net FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetLiabilityTransfersNet	-31000000	USD
CY2012	aee	Gain Loss Recognized Related To Valuation Adjustments For Counterparty Default Risk GainLossRecognizedRelatedToValuationAdjustmentsForCounterpartyDefaultRisk	-1000000	USD
CY2010	aee	Gain Loss Recognized Related To Valuation Adjustments For Counterparty Default Risk GainLossRecognizedRelatedToValuationAdjustmentsForCounterpartyDefaultRisk	1000000	USD
CY2011	aee	Gain Loss Recognized Related To Valuation Adjustments For Counterparty Default Risk GainLossRecognizedRelatedToValuationAdjustmentsForCounterpartyDefaultRisk	-2000000	USD
CY2010	aee	Generator Advances For Construction Refunded Net Of Receipts GeneratorAdvancesForConstructionRefundedNetOfReceipts	-39000000	USD
CY2011	aee	Generator Advances For Construction Refunded Net Of Receipts GeneratorAdvancesForConstructionRefundedNetOfReceipts	-73000000	USD
CY2012	aee	Generator Advances For Construction Refunded Net Of Receipts GeneratorAdvancesForConstructionRefundedNetOfReceipts		USD
CY2012Q4	aee	Insurance Aggregate Maximum Coverage InsuranceAggregateMaximumCoverage	12594000000	USD
CY2012Q4	aee	Insurance Maximum Coverage Per Incident InsuranceMaximumCoveragePerIncident	118000000	USD
CY2011Q4	aee	Letters Of Credit Held As Collateral LettersOfCreditHeldAsCollateral	9000000	USD
CY2012Q4	aee	Letters Of Credit Held As Collateral LettersOfCreditHeldAsCollateral	7000000	USD
CY2012	aee	Losses In Excess Of Primary Coverage LossesInExcessOfPrimaryCoverage	500000000	USD
CY2012	aee	Maximum Annual Payment In Calendar Year Per Reactor Incident Under Price Andersen Liability Provisions Of Atomic Energy Act MaximumAnnualPaymentInCalendarYearPerReactorIncidentUnderPriceAndersenLiabilityProvisionsOfAtomicEnergyAct	17500000	USD
CY2012	aee	Maximum Annual Payment Per Incident At Licensed Commercia Lnuclear Reactor MaximumAnnualPaymentPerIncidentAtLicensedCommerciaLnuclearReactor	17500000	USD
CY2012	aee	Missouri Public Service Commission Requirement To File Updated Cost Study And Funding Analysis For Decommissioning Energy Center Period MissouriPublicServiceCommissionRequirementToFileUpdatedCostStudyAndFundingAnalysisForDecommissioningEnergyCenterPeriod	P3Y
CY2012	aee	Number Of Additional Weeks After Initial Indemnity Coverage For Power Outage NumberOfAdditionalWeeksAfterInitialIndemnityCoverageForPowerOutage	P71W
CY2012Q4	aee	Number Of Combustion Turbine Electric Generation Equipment Under Capital Lease Agreements NumberOfCombustionTurbineElectricGenerationEquipmentUnderCapitalLeaseAgreements	2	equipment
CY2011Q4	aee	Number Of Combustion Turbine Electric Generation Equipment Under Capital Lease Agreements NumberOfCombustionTurbineElectricGenerationEquipmentUnderCapitalLeaseAgreements	2	equipment
CY2012	aee	Number Of States Participating In Cap And Trade Program NumberOfStatesParticipatingInCapAndTradeProgram	28	state
CY2012	aee	Number Of Weeks Of Coverage After First Eight Weeks Of Outage NumberOfWeeksOfCoverageAfterFirstEightWeeksOfOutage	P52W
CY2012	aee	Number Of Years Limit Of Liability And Maximum Potential Annual Payments Are Adjusted NumberOfYearsLimitOfLiabilityAndMaximumPotentialAnnualPaymentsAreAdjusted	P5Y
CY2012	aee	Nwf Fee Number Of Mills NwfFeeNumberOfMills	1	mill
CY2011	aee	Payment Of Accrued Interest PaymentOfAccruedInterest	1000000	USD
CY2012	aee	Percent Of Top Performing Facilities PercentOfTopPerformingFacilities	0.12
CY2011	aee	Premium Related To Debt Redemptions PremiumRelatedToDebtRedemptions		USD
CY2010	aee	Premium Related To Debt Redemptions PremiumRelatedToDebtRedemptions		USD
CY2012	aee	Premium Related To Debt Redemptions PremiumRelatedToDebtRedemptions	-138000000	USD
CY2011Q4	aee	Property Plant And Equipment Net Before Construction Work In Progress PropertyPlantAndEquipmentNetBeforeConstructionWorkInProgress	17039000000	USD
CY2012Q4	aee	Property Plant And Equipment Net Before Construction Work In Progress PropertyPlantAndEquipmentNetBeforeConstructionWorkInProgress	15086000000	USD
CY2012Q4	aee	Property Plant And Equipment Number Of Capital Lease Agreements PropertyPlantAndEquipmentNumberOfCapitalLeaseAgreements	2
CY2011Q4	aee	Property Plant And Equipment Number Of Capital Lease Agreements PropertyPlantAndEquipmentNumberOfCapitalLeaseAgreements	2
CY2012Q4	aee	Receivables Payables And Accrued Income Net ReceivablesPayablesAndAccruedIncomeNet	2000000	USD
CY2011Q4	aee	Receivables Payables And Accrued Income Net ReceivablesPayablesAndAccruedIncomeNet	-1000000	USD
CY2012Q4	aee	Related Party Transaction Guarantees Outstanding RelatedPartyTransactionGuaranteesOutstanding	354000000	USD
CY2013Q1	dei	Entity Common Stock Shares Outstanding EntityCommonStockSharesOutstanding	242634671	shares
CY2012	dei	Entity Current Reporting Status EntityCurrentReportingStatus	Yes
CY2012	dei	Entity Filer Category EntityFilerCategory	Large Accelerated Filer
CY2012	aee	Tax Credit Carryforward Change In Valuation Allowance TaxCreditCarryforwardChangeInValuationAllowance	2000000	USD
CY2011	aee	Tax Grants Received Related To Renewable Energy Properties TaxGrantsReceivedRelatedToRenewableEnergyProperties		USD
CY2010	aee	Tax Grants Received Related To Renewable Energy Properties TaxGrantsReceivedRelatedToRenewableEnergyProperties		USD
CY2012	aee	Tax Grants Received Related To Renewable Energy Properties TaxGrantsReceivedRelatedToRenewableEnergyProperties	18000000	USD
CY2012	aee	Transfers Into Assets And Liabilities Classified As Fair Value Inputs Level3 And Transfers Out Of Assets And Liabilities Classified As Fair Value Inputs Level2 TransfersIntoAssetsAndLiabilitiesClassifiedAsFairValueInputsLevel3AndTransfersOutOfAssetsAndLiabilitiesClassifiedAsFairValueInputsLevel2		USD
CY2011	aee	Transfers Into Assets And Liabilities Classified As Fair Value Inputs Level3 And Transfers Out Of Assets And Liabilities Classified As Fair Value Inputs Level2 TransfersIntoAssetsAndLiabilitiesClassifiedAsFairValueInputsLevel3AndTransfersOutOfAssetsAndLiabilitiesClassifiedAsFairValueInputsLevel2		USD
CY2012	dei	Amendment Flag AmendmentFlag	false
CY2012	dei	Current Fiscal Year End Date CurrentFiscalYearEndDate	--12-31
CY2012	dei	Document Fiscal Period Focus DocumentFiscalPeriodFocus	FY
CY2012	dei	Document Fiscal Year Focus DocumentFiscalYearFocus	2012
CY2012	dei	Document Period End Date DocumentPeriodEndDate	2012-12-31
CY2012	dei	Document Type DocumentType	10-K
CY2012	dei	Entity Central Index Key EntityCentralIndexKey	0001002910
CY2012	dei	Entity Voluntary Filers EntityVoluntaryFilers	No
CY2012	dei	Entity Well Known Seasoned Issuer EntityWellKnownSeasonedIssuer	Yes
CY2012	dei	Trading Symbol TradingSymbol	AEE

Files In Submission

Name	View Source	Status
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0001445305-13-000414-index.html	Edgar Link	pending
0001445305-13-000414.txt	Edgar Link	pending
0001445305-13-000414-xbrl.zip	Edgar Link	pending
aee-20121231.xml	Edgar Link	completed
aee-20121231.xsd	Edgar Link	pending
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aee-20121231_def.xml	Edgar Link	unprocessable
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$AEE
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2010 Q4 Form 10-K Financial Statement

#000144530513000414 Filed on March 01, 2013

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$AEE AMEREN CORP Stock $aee

2010 Q4 Form 10-K Financial Statement

#000144530513000414 Filed on March 01, 2013

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$AEE
AMEREN CORP Stock $aee