$LNT
ALLIANT ENERGY CORP Stock $lnt

$lnt Overview Financials Valuation SEC Filings Company Website

2012 Form 10-K Financial Statement

#000035254113000007 Filed on February 26, 2013

Income Statement

Concept	2012	2011 Q4	2011 Q3
Revenue	$3.095B	$760.8M	$870.9M
YoY Change	-3.94%	-8.62%	-8.49%
Cost Of Revenue	$488.7M	$136.2M	$100.0M
YoY Change	-11.53%	-13.25%	-5.48%
Gross Profit	$2.606B	$624.6M	$770.9M
YoY Change	-2.37%	-7.55%	-8.87%
Gross Profit Margin	84.21%	82.1%	88.52%
Selling, General & Admin
YoY Change
% of Gross Profit
Research & Development
YoY Change
% of Gross Profit
Depreciation & Amortization	$332.9M	$81.50M	$81.30M
YoY Change	2.81%	6.68%	7.68%
% of Gross Profit	12.78%	13.05%	10.55%
Operating Expenses	$2.086B	$518.6M	$561.5M
YoY Change	-3.23%	-9.93%	-6.31%
Operating Profit	$519.7M	$106.0M	$209.4M
YoY Change	1.25%	6.21%	-15.09%
Interest Expense	$156.7M	-$23.40M	$38.80M
YoY Change	-1.01%	-5.26%	-243.7%
% of Operating Profit	30.15%	-22.08%	18.53%
Other Income/Expense, Net	-$89.50M		-$25.30M
YoY Change	-12.85%
Pretax Income	$430.2M	$82.60M	$184.1M
YoY Change	4.77%	9.99%	-16.17%
Income Tax	$89.40M	$14.70M	$43.30M
% Of Pretax Income	20.78%	17.8%	23.52%
Net Earnings	$335.7M	$61.00M	$125.9M
YoY Change	4.29%	17.31%	-18.09%
Net Earnings / Revenue	10.85%	8.02%	14.46%
Basic Earnings Per Share
Diluted Earnings Per Share	$1.516M	$0.51	$1.10
COMMON SHARES
Basic Shares Outstanding	110.8M shares		110.6M shares
Diluted Shares Outstanding	110.8M shares		110.7M shares

Balance Sheet

Concept	2012	2011 Q4	2011 Q3
SHORT-TERM ASSETS
Cash & Short-Term Investments	$21.00M	$11.00M	$46.00M
YoY Change	90.91%	-93.08%	-66.42%
Cash & Equivalents	$21.00M	$11.40M	$45.70M
Short-Term Investments
Other Short-Term Assets	$446.0M	$37.70M	$303.0M
YoY Change	11.78%	-88.51%	-10.62%
Inventory	$204.0M	$218.0M	$205.0M
Prepaid Expenses
Receivables	$304.0M	$88.10M	$345.0M
Other Receivables	$19.00M	$39.00M	$48.00M
Total Short-Term Assets	$994.0M	$870.6M	$947.0M
YoY Change	14.12%	-20.35%	-18.92%
LONG-TERM ASSETS
Property, Plant & Equipment	$7.838B	$7.033B	$6.938B
YoY Change	11.45%	4.49%	5.81%
Goodwill
YoY Change
Intangibles
YoY Change
Long-Term Investments	$319.0M	$249.6M	$299.0M
YoY Change	5.98%	4.65%	4.18%
Other Assets	$1.634B	$91.90M	$1.295B
YoY Change	10.18%	-91.91%	10.03%
Total Long-Term Assets	$9.792B	$8.817B	$8.534B
YoY Change	11.06%	7.66%	5.91%
TOTAL ASSETS
Total Short-Term Assets	$994.0M	$870.6M	$947.0M
Total Long-Term Assets	$9.792B	$8.817B	$8.534B
Total Assets	$10.79B	$9.688B	$9.481B
YoY Change	11.33%	4.36%	2.76%
SHORT-TERM LIABILITIES
YoY Change
Accounts Payable	$339.0M	$267.8M	$315.0M
YoY Change	26.49%	-20.3%	6.78%
Accrued Expenses	$48.00M	$47.00M	$47.00M
YoY Change	2.13%	0.0%	0.0%
Deferred Revenue
YoY Change
Short-Term Debt	$218.0M	$103.0M	$22.00M
YoY Change	111.65%	119.15%
Long-Term Debt Due	$2.000M	$1.400M	$1.000M
YoY Change	100.0%	40.0%	0.0%
Total Short-Term Liabilities	$1.020B	$855.2M	$774.0M
YoY Change	19.3%	-1.36%	11.85%
LONG-TERM LIABILITIES
Long-Term Debt	$3.137B	$2.703B	$2.704B
YoY Change	16.06%	0.0%	0.0%
Other Long-Term Liabilities	$1.353B	$259.4M	$1.234B
YoY Change	2.66%	-77.23%	-5.95%
Total Long-Term Liabilities	$4.490B	$2.963B	$3.938B
YoY Change	11.66%	-22.89%	-1.94%
TOTAL LIABILITIES
Total Short-Term Liabilities	$1.020B	$855.2M	$774.0M
Total Long-Term Liabilities	$4.490B	$2.963B	$3.938B
Total Liabilities	$7.446B	$3.818B	$6.275B
YoY Change	15.09%	-37.88%	2.97%
SHAREHOLDERS EQUITY
Retained Earnings		$1.510B
YoY Change
Common Stock		$1.512B
YoY Change
Preferred Stock
YoY Change
Treasury Stock (at cost)
YoY Change
Treasury Stock Shares
Shareholders Equity	$3.340B	$3.013B	$3.207B
YoY Change
Total Liabilities & Shareholders Equity	$10.79B	$9.688B	$9.481B
YoY Change	11.33%	4.36%	2.76%

Cashflow Statement

Concept	2012	2011 Q4	2011 Q3
OPERATING ACTIVITIES
Net Income	$335.7M	$61.00M	$125.9M
YoY Change	4.29%	17.31%	-18.09%
Depreciation, Depletion And Amortization	$332.9M	$81.50M	$81.30M
YoY Change	2.81%	6.68%	7.68%
Cash From Operating Activities	$841.1M	$90.00M	$145.9M
YoY Change	19.7%	-68.89%	-32.58%
INVESTING ACTIVITIES
Capital Expenditures	$1.158B	-$127.9M	-$142.1M
YoY Change	71.98%	-47.94%	-29.93%
Acquisitions
YoY Change
Other Investing Activities	-$2.600M	-$17.80M	-$23.20M
YoY Change	-126.8%	24.48%	186.42%
Cash From Investing Activities	-$1.156B	-$145.7M	-$165.3M
YoY Change	77.2%	-43.96%	-21.62%
FINANCING ACTIVITIES
Cash Dividend Paid
YoY Change
Common Stock Issuance & Retirement, Net
YoY Change
Debt Paid & Issued, Net	$1.400M
YoY Change	7.69%
Cash From Financing Activities	$324.2M	21.40M	-12.00M
YoY Change	-263.32%	-405.71%	-69.7%
NET CHANGE
Cash From Operating Activities	$841.1M	90.00M	145.9M
Cash From Investing Activities	-$1.156B	-145.7M	-165.3M
Cash From Financing Activities	$324.2M	21.40M	-12.00M
Net Change In Cash	$9.800M	-34.30M	-31.40M
YoY Change	-106.63%	-253.81%	-7.92%
FREE CASH FLOW
Cash From Operating Activities	$841.1M	$90.00M	$145.9M
Capital Expenditures	$1.158B	-$127.9M	-$142.1M
Free Cash Flow	-$317.0M	$217.9M	$288.0M
YoY Change	-1181.91%	-59.27%	-31.3%

Facts In Submission

Frame	Concept Type	Concept / XBRL Key	Value	Unit
CY2011Q4	us-gaap	Accounts Payable Current AccountsPayableCurrent	267800000	USD
CY2012Q4	us-gaap	Accounts Payable Current AccountsPayableCurrent	339300000	USD
CY2012Q4	us-gaap	Accounts Receivable Net Current AccountsReceivableNetCurrent	94900000	USD
CY2011Q4	us-gaap	Accounts Receivable Net Current AccountsReceivableNetCurrent	88100000	USD
CY2012Q4	us-gaap	Accrual For Environmental Loss Contingencies AccrualForEnvironmentalLossContingencies	29000000	USD
CY2011Q4	us-gaap	Accrual For Environmental Loss Contingencies AccrualForEnvironmentalLossContingencies	33600000	USD
CY2011Q4	us-gaap	Accrued Environmental Loss Contingencies Current AccruedEnvironmentalLossContingenciesCurrent	4800000	USD
CY2012Q4	us-gaap	Accrued Environmental Loss Contingencies Current AccruedEnvironmentalLossContingenciesCurrent	3700000	USD
CY2012Q4	us-gaap	Accrued Environmental Loss Contingencies Noncurrent AccruedEnvironmentalLossContingenciesNoncurrent	25300000	USD
CY2011Q4	us-gaap	Accrued Environmental Loss Contingencies Noncurrent AccruedEnvironmentalLossContingenciesNoncurrent	28800000	USD
CY2012Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-800000	USD
CY2011Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-800000	USD
CY2012Q4	us-gaap	Additional Collateral Aggregate Fair Value AdditionalCollateralAggregateFairValue	39900000	USD
CY2012Q4	us-gaap	Additional Paid In Capital Common Stock AdditionalPaidInCapitalCommonStock	1511200000	USD
CY2011Q4	us-gaap	Additional Paid In Capital Common Stock AdditionalPaidInCapitalCommonStock	1510800000	USD
CY2010	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	7500000	USD
CY2012	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	6900000	USD
CY2011	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	10100000	USD
CY2012	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	0	USD
CY2011	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	13400000	USD
CY2010	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	16500000	USD
CY2011Q4	us-gaap	Amount Of Impairment To Carrying Amount Of Regulatory Assets AmountOfImpairmentToCarryingAmountOfRegulatoryAssets	9000000	USD
CY2011Q4	us-gaap	Asset Retirement Obligation AssetRetirementObligation	91100000	USD
CY2010Q4	us-gaap	Asset Retirement Obligation AssetRetirementObligation	75900000	USD
CY2012Q4	us-gaap	Asset Retirement Obligation AssetRetirementObligation	101500000	USD
CY2011	us-gaap	Asset Retirement Obligation Accretion Expense AssetRetirementObligationAccretionExpense	4300000	USD
CY2012	us-gaap	Asset Retirement Obligation Accretion Expense AssetRetirementObligationAccretionExpense	3400000	USD
CY2012	us-gaap	Asset Retirement Obligation Liabilities Incurred AssetRetirementObligationLiabilitiesIncurred	16800000	USD
CY2011	us-gaap	Asset Retirement Obligation Liabilities Incurred AssetRetirementObligationLiabilitiesIncurred	4000000	USD
CY2011	us-gaap	Asset Retirement Obligation Liabilities Settled AssetRetirementObligationLiabilitiesSettled	900000	USD
CY2012	us-gaap	Asset Retirement Obligation Liabilities Settled AssetRetirementObligationLiabilitiesSettled	3400000	USD
CY2011	us-gaap	Asset Retirement Obligation Revision Of Estimate AssetRetirementObligationRevisionOfEstimate	7800000	USD
CY2012	us-gaap	Asset Retirement Obligation Revision Of Estimate AssetRetirementObligationRevisionOfEstimate	-6400000	USD
CY2012Q4	us-gaap	Assets Assets	10785500000	USD
CY2011Q4	us-gaap	Assets Assets	9687900000	USD
CY2010Q4	us-gaap	Assets Assets	9282900000	USD
CY2012Q4	us-gaap	Assets Current AssetsCurrent	994300000	USD
CY2011Q4	us-gaap	Assets Current AssetsCurrent	870600000	USD
CY2012Q4	us-gaap	Assets Held For Sale Current AssetsHeldForSaleCurrent	27900000	USD
CY2011Q4	us-gaap	Assets Held For Sale Current AssetsHeldForSaleCurrent	119600000	USD
CY2011Q4	us-gaap	Assets Of Disposal Group Including Discontinued Operation AssetsOfDisposalGroupIncludingDiscontinuedOperation	57500000	USD
CY2012Q4	us-gaap	Assets Of Disposal Group Including Discontinued Operation AssetsOfDisposalGroupIncludingDiscontinuedOperation	-3500000	USD
CY2012Q4	us-gaap	Assets Of Disposal Group Including Discontinued Operation Current AssetsOfDisposalGroupIncludingDiscontinuedOperationCurrent	27900000	USD
CY2011Q4	us-gaap	Assets Of Disposal Group Including Discontinued Operation Current AssetsOfDisposalGroupIncludingDiscontinuedOperationCurrent	115500000	USD
CY2011	us-gaap	Capital Expenditures Incurred But Not Yet Paid CapitalExpendituresIncurredButNotYetPaid	49700000	USD
CY2012	us-gaap	Capital Expenditures Incurred But Not Yet Paid CapitalExpendituresIncurredButNotYetPaid	105300000	USD
CY2010	us-gaap	Capital Expenditures Incurred But Not Yet Paid CapitalExpendituresIncurredButNotYetPaid	75000000	USD
CY2011Q4	us-gaap	Capitalization Longterm Debt And Equity CapitalizationLongtermDebtAndEquity	5923000000	USD
CY2012Q4	us-gaap	Capitalization Longterm Debt And Equity CapitalizationLongtermDebtAndEquity	6478400000	USD
CY2012Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	21200000	USD
CY2011Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	11400000	USD
CY2010Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	159300000	USD
CY2009Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	175300000	USD
CY2012	us-gaap	Cash And Cash Equivalents Period Increase Decrease CashAndCashEquivalentsPeriodIncreaseDecrease	9800000	USD
CY2010	us-gaap	Cash And Cash Equivalents Period Increase Decrease CashAndCashEquivalentsPeriodIncreaseDecrease	-16000000	USD
CY2011	us-gaap	Cash And Cash Equivalents Period Increase Decrease CashAndCashEquivalentsPeriodIncreaseDecrease	-147900000	USD
CY2011Q4	us-gaap	Cash Surrender Value Of Life Insurance CashSurrenderValueOfLifeInsurance	49200000	USD
CY2012Q4	us-gaap	Cash Surrender Value Of Life Insurance CashSurrenderValueOfLifeInsurance	50500000	USD
CY2012Q4	us-gaap	Class Of Warrant Or Right Exercise Price Of Warrants Or Rights ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights	110
CY2012Q4	us-gaap	Commercial Paper CommercialPaper	217500000	USD
CY2011Q4	us-gaap	Commercial Paper CommercialPaper	102800000	USD
CY2012	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	1.80
CY2011	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	1.70
CY2010	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	1.58
CY2012	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	1.80
CY2010	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	1.58
CY2011	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	1.70
CY2011Q4	us-gaap	Common Stock Held In Trust CommonStockHeldInTrust	8300000	USD
CY2012Q4	us-gaap	Common Stock Held In Trust CommonStockHeldInTrust	7300000	USD
CY2012Q4	us-gaap	Common Stock Par Or Stated Value Per Share CommonStockParOrStatedValuePerShare	0.01
CY2011Q4	us-gaap	Common Stock Par Or Stated Value Per Share CommonStockParOrStatedValuePerShare	0.01
CY2012Q4	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	240000000	shares
CY2011Q4	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	240000000	shares
CY2011Q4	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	111018821	shares
CY2012Q4	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	110987400	shares
CY2010Q4	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	110893901	shares
CY2009Q4	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	110656498	shares
CY2011Q4	us-gaap	Common Stock Value CommonStockValue	1100000	USD
CY2012Q4	us-gaap	Common Stock Value CommonStockValue	1100000	USD
CY2011	us-gaap	Cost Of Transmission CostOfTransmission	323800000	USD
CY2012	us-gaap	Cost Of Transmission CostOfTransmission	341300000	USD
CY2010	us-gaap	Cost Of Transmission CostOfTransmission	279500000	USD
CY2010	us-gaap	Costs And Expenses CostsAndExpenses	2702100000	USD
CY2011	us-gaap	Costs And Expenses CostsAndExpenses	2708100000	USD
CY2012	us-gaap	Costs And Expenses CostsAndExpenses	2574800000	USD
CY2011Q4	us-gaap	Costs In Excess Of Billings On Uncompleted Contracts Or Programs Expected To Be Collected Within One Year CostsInExcessOfBillingsOnUncompletedContractsOrProgramsExpectedToBeCollectedWithinOneYear	75100000	USD
CY2012Q4	us-gaap	Costs In Excess Of Billings On Uncompleted Contracts Or Programs Expected To Be Collected Within One Year CostsInExcessOfBillingsOnUncompletedContractsOrProgramsExpectedToBeCollectedWithinOneYear	81400000	USD
CY2010	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	7100000	USD
CY2012	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	-29300000	USD
CY2011	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	58600000	USD
CY2010	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	10600000	USD
CY2012	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	11600000	USD
CY2011	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	15700000	USD
CY2012Q4	us-gaap	Debt Instrument Fair Value DebtInstrumentFairValue	3860500000	USD
CY2012Q4	us-gaap	Debt Instrument Unamortized Discount Premium Net DebtInstrumentUnamortizedDiscountPremiumNet	-11800000	USD
CY2011Q4	us-gaap	Debt Instrument Unamortized Discount Premium Net DebtInstrumentUnamortizedDiscountPremiumNet	-11800000	USD
CY2012	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	157800000	USD
CY2011	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	99000000	USD
CY2010	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	165500000	USD
CY2011Q4	us-gaap	Deferred Income Tax Liabilities DeferredIncomeTaxLiabilities	2320400000	USD
CY2012Q4	us-gaap	Deferred Income Tax Liabilities DeferredIncomeTaxLiabilities	2507000000	USD
CY2012	us-gaap	Deferred Income Taxes And Tax Credits DeferredIncomeTaxesAndTaxCredits	143300000	USD
CY2011	us-gaap	Deferred Income Taxes And Tax Credits DeferredIncomeTaxesAndTaxCredits	10200000	USD
CY2010	us-gaap	Deferred Income Taxes And Tax Credits DeferredIncomeTaxesAndTaxCredits	216600000	USD
CY2012	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	23900000	USD
CY2011	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	-16800000	USD
CY2010	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	4900000	USD
CY2011Q4	us-gaap	Deferred Tax Assets Net DeferredTaxAssetsNet	751000000	USD
CY2012Q4	us-gaap	Deferred Tax Assets Net DeferredTaxAssetsNet	743000000	USD
CY2011Q4	us-gaap	Deferred Tax Assets Net Current DeferredTaxAssetsNetCurrent	22800000	USD
CY2012Q4	us-gaap	Deferred Tax Assets Net Current DeferredTaxAssetsNetCurrent	170200000	USD
CY2012Q4	us-gaap	Deferred Tax Assets Operating Loss Carryforwards DeferredTaxAssetsOperatingLossCarryforwards	487000000	USD
CY2011Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	1200000	USD
CY2012Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	1900000	USD
CY2011Q4	us-gaap	Deferred Tax Liabilities DeferredTaxLiabilities	1569400000	USD
CY2012Q4	us-gaap	Deferred Tax Liabilities DeferredTaxLiabilities	1764000000	USD
CY2011Q4	us-gaap	Deferred Tax Liabilities Noncurrent DeferredTaxLiabilitiesNoncurrent	1592200000	USD
CY2012Q4	us-gaap	Deferred Tax Liabilities Noncurrent DeferredTaxLiabilitiesNoncurrent	1934200000	USD
CY2011Q4	us-gaap	Defined Benefit Plan Assumptions Used Calculating Benefit Obligation Discount Rate DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate	0.0520
CY2012	us-gaap	Defined Benefit Plan Effect Of One Percentage Point Decrease On Accumulated Postretirement Benefit Obligation1 DefinedBenefitPlanEffectOfOnePercentagePointDecreaseOnAccumulatedPostretirementBenefitObligation1	2400000	USD
CY2012	us-gaap	Defined Benefit Plan Effect Of One Percentage Point Decrease On Service And Interest Cost Components1 DefinedBenefitPlanEffectOfOnePercentagePointDecreaseOnServiceAndInterestCostComponents1	400000	USD
CY2012	us-gaap	Defined Benefit Plan Effect Of One Percentage Point Increase On Accumulated Postretirement Benefit Obligation DefinedBenefitPlanEffectOfOnePercentagePointIncreaseOnAccumulatedPostretirementBenefitObligation	2600000	USD
CY2012	us-gaap	Defined Benefit Plan Effect Of One Percentage Point Increase On Service And Interest Cost Components DefinedBenefitPlanEffectOfOnePercentagePointIncreaseOnServiceAndInterestCostComponents	400000	USD
CY2012Q4	us-gaap	Defined Benefit Plan Expected Future Benefit Payments Five Fiscal Years Thereafter DefinedBenefitPlanExpectedFutureBenefitPaymentsFiveFiscalYearsThereafter	458300000	USD
CY2012Q4	us-gaap	Defined Benefit Plan Expected Future Benefit Payments Next Twelve Months DefinedBenefitPlanExpectedFutureBenefitPaymentsNextTwelveMonths	78500000	USD
CY2012Q4	us-gaap	Defined Benefit Plan Expected Future Benefit Payments Year Five DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFive	85800000	USD
CY2012Q4	us-gaap	Defined Benefit Plan Expected Future Benefit Payments Year Four DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFour	83000000	USD
CY2012Q4	us-gaap	Defined Benefit Plan Expected Future Benefit Payments Year Three DefinedBenefitPlanExpectedFutureBenefitPaymentsYearThree	84800000	USD
CY2012Q4	us-gaap	Defined Benefit Plan Expected Future Benefit Payments Year Two DefinedBenefitPlanExpectedFutureBenefitPaymentsYearTwo	80900000	USD
CY2011	us-gaap	Defined Contribution Plan Cost Recognized DefinedContributionPlanCostRecognized	18400000	USD
CY2010	us-gaap	Defined Contribution Plan Cost Recognized DefinedContributionPlanCostRecognized	18500000	USD
CY2012	us-gaap	Defined Contribution Plan Cost Recognized DefinedContributionPlanCostRecognized	18500000	USD
CY2011	us-gaap	Depreciation And Amortization DepreciationAndAmortization	321000000	USD
CY2010	us-gaap	Depreciation And Amortization DepreciationAndAmortization	287300000	USD
CY2012	us-gaap	Depreciation And Amortization DepreciationAndAmortization	332400000	USD
CY2012Q4	us-gaap	Derivative Liabilities Current DerivativeLiabilitiesCurrent	31100000	USD
CY2011Q4	us-gaap	Derivative Liabilities Current DerivativeLiabilitiesCurrent	55900000	USD
CY2012Q4	us-gaap	Derivative Net Liability Position Aggregate Fair Value DerivativeNetLiabilityPositionAggregateFairValue	40400000	USD
CY2011	us-gaap	Discontinued Operation Income Loss From Discontinued Operation Before Income Tax DiscontinuedOperationIncomeLossFromDiscontinuedOperationBeforeIncomeTax	-31900000	USD
CY2012	us-gaap	Discontinued Operation Income Loss From Discontinued Operation Before Income Tax DiscontinuedOperationIncomeLossFromDiscontinuedOperationBeforeIncomeTax	-8500000	USD
CY2010	us-gaap	Discontinued Operation Income Loss From Discontinued Operation Before Income Tax DiscontinuedOperationIncomeLossFromDiscontinuedOperationBeforeIncomeTax	-7500000	USD
CY2011	us-gaap	Discontinued Operation Tax Effect Of Discontinued Operation DiscontinuedOperationTaxEffectOfDiscontinuedOperation	-12400000	USD
CY2010	us-gaap	Discontinued Operation Tax Effect Of Discontinued Operation DiscontinuedOperationTaxEffectOfDiscontinuedOperation	-3600000	USD
CY2012	us-gaap	Discontinued Operation Tax Effect Of Discontinued Operation DiscontinuedOperationTaxEffectOfDiscontinuedOperation	-3400000	USD
CY2012	us-gaap	Disposal Group Including Discontinued Operation Operating Expense DisposalGroupIncludingDiscontinuedOperationOperatingExpense	297000000	USD
CY2011	us-gaap	Disposal Group Including Discontinued Operation Operating Expense DisposalGroupIncludingDiscontinuedOperationOperatingExpense	476900000	USD
CY2010	us-gaap	Disposal Group Including Discontinued Operation Operating Expense DisposalGroupIncludingDiscontinuedOperationOperatingExpense	166800000	USD
CY2011Q4	us-gaap	Disposal Group Including Discontinued Operation Other Assets DisposalGroupIncludingDiscontinuedOperationOtherAssets	300000	USD
CY2012Q4	us-gaap	Disposal Group Including Discontinued Operation Other Assets DisposalGroupIncludingDiscontinuedOperationOtherAssets	0	USD
CY2012Q4	us-gaap	Disposal Group Including Discontinued Operation Other Noncurrent Liabilities DisposalGroupIncludingDiscontinuedOperationOtherNoncurrentLiabilities	0	USD
CY2011Q4	us-gaap	Disposal Group Including Discontinued Operation Other Noncurrent Liabilities DisposalGroupIncludingDiscontinuedOperationOtherNoncurrentLiabilities	100000	USD
CY2011Q4	us-gaap	Disposal Group Including Discontinued Operation Property Plant And Equipment Net DisposalGroupIncludingDiscontinuedOperationPropertyPlantAndEquipmentNet	3800000	USD
CY2012Q4	us-gaap	Disposal Group Including Discontinued Operation Property Plant And Equipment Net DisposalGroupIncludingDiscontinuedOperationPropertyPlantAndEquipmentNet	0	USD
CY2010	us-gaap	Disposal Group Including Discontinued Operation Revenue DisposalGroupIncludingDiscontinuedOperationRevenue	160300000	USD
CY2012	us-gaap	Disposal Group Including Discontinued Operation Revenue DisposalGroupIncludingDiscontinuedOperationRevenue	289200000	USD
CY2011	us-gaap	Disposal Group Including Discontinued Operation Revenue DisposalGroupIncludingDiscontinuedOperationRevenue	445000000	USD
CY2011	us-gaap	Dividends Common Stock DividendsCommonStock	188100000	USD
CY2012	us-gaap	Dividends Common Stock DividendsCommonStock	199300000	USD
CY2010	us-gaap	Dividends Common Stock DividendsCommonStock	174600000	USD
CY2011	us-gaap	Dividends Preferred Stock DividendsPreferredStock	18300000	USD
CY2010	us-gaap	Dividends Preferred Stock DividendsPreferredStock	18700000	USD
CY2012	us-gaap	Dividends Preferred Stock DividendsPreferredStock	15900000	USD
CY2012	us-gaap	Earnings Per Share Basic And Diluted EarningsPerShareBasicAndDiluted	2.89
CY2011	us-gaap	Earnings Per Share Basic And Diluted EarningsPerShareBasicAndDiluted	2.74
CY2010	us-gaap	Earnings Per Share Basic And Diluted EarningsPerShareBasicAndDiluted	2.60
CY2012Q4	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.62
CY2011Q4	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.51
CY2012Q1	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.32
CY2011Q2	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.46
CY2011Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.10
CY2012Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.36
CY2012Q2	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.60
CY2011Q1	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.66
CY2011	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.169
CY2010	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.323
CY2012	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.208
CY2012	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.350
CY2011	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.350
CY2010	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.350
CY2010	us-gaap	Effective Income Tax Rate Reconciliation Deductions Medicare Prescription Drug Benefit EffectiveIncomeTaxRateReconciliationDeductionsMedicarePrescriptionDrugBenefit	0.016
CY2012	us-gaap	Effective Income Tax Rate Reconciliation Deductions Medicare Prescription Drug Benefit EffectiveIncomeTaxRateReconciliationDeductionsMedicarePrescriptionDrugBenefit	0.000
CY2011	us-gaap	Effective Income Tax Rate Reconciliation Deductions Medicare Prescription Drug Benefit EffectiveIncomeTaxRateReconciliationDeductionsMedicarePrescriptionDrugBenefit	0.000
CY2012	us-gaap	Effective Income Tax Rate Reconciliation Deductions Qualified Production Activities EffectiveIncomeTaxRateReconciliationDeductionsQualifiedProductionActivities	0.058
CY2010	us-gaap	Effective Income Tax Rate Reconciliation Deductions Qualified Production Activities EffectiveIncomeTaxRateReconciliationDeductionsQualifiedProductionActivities	0.024
CY2011	us-gaap	Effective Income Tax Rate Reconciliation Deductions Qualified Production Activities EffectiveIncomeTaxRateReconciliationDeductionsQualifiedProductionActivities	0.066
CY2011	us-gaap	Effective Income Tax Rate Reconciliation Other Adjustments EffectiveIncomeTaxRateReconciliationOtherAdjustments	-0.009
CY2010	us-gaap	Effective Income Tax Rate Reconciliation Other Adjustments EffectiveIncomeTaxRateReconciliationOtherAdjustments	-0.028
CY2012	us-gaap	Effective Income Tax Rate Reconciliation Other Adjustments EffectiveIncomeTaxRateReconciliationOtherAdjustments	-0.014
CY2011	us-gaap	Effective Income Tax Rate Reconciliation Prior Year Income Taxes EffectiveIncomeTaxRateReconciliationPriorYearIncomeTaxes	0.002
CY2010	us-gaap	Effective Income Tax Rate Reconciliation Prior Year Income Taxes EffectiveIncomeTaxRateReconciliationPriorYearIncomeTaxes	0.003
CY2012	us-gaap	Effective Income Tax Rate Reconciliation Prior Year Income Taxes EffectiveIncomeTaxRateReconciliationPriorYearIncomeTaxes	0.000
CY2011	us-gaap	Effective Income Tax Rate Reconciliation State And Local Income Taxes EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes	0.046
CY2012	us-gaap	Effective Income Tax Rate Reconciliation State And Local Income Taxes EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes	0.057
CY2010	us-gaap	Effective Income Tax Rate Reconciliation State And Local Income Taxes EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes	0.048
CY2010	us-gaap	Electric Domestic Regulated Revenue ElectricDomesticRegulatedRevenue	2674200000	USD
CY2012	us-gaap	Electric Domestic Regulated Revenue ElectricDomesticRegulatedRevenue	2589300000	USD
CY2011	us-gaap	Electric Domestic Regulated Revenue ElectricDomesticRegulatedRevenue	2635800000	USD
CY2012Q4	us-gaap	Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized	6100000	USD
CY2010	us-gaap	Employee Service Share Based Compensation Tax Benefit From Compensation Expense EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense	3000000	USD
CY2012	us-gaap	Employee Service Share Based Compensation Tax Benefit From Compensation Expense EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense	2800000	USD
CY2011	us-gaap	Employee Service Share Based Compensation Tax Benefit From Compensation Expense EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense	4000000	USD
CY2012Q4	us-gaap	Energy Related Inventory Gas Stored Underground EnergyRelatedInventoryGasStoredUnderground	37700000	USD
CY2011Q4	us-gaap	Energy Related Inventory Gas Stored Underground EnergyRelatedInventoryGasStoredUnderground	57700000	USD
CY2012Q4	us-gaap	Energy Related Inventory Other Fossil Fuel EnergyRelatedInventoryOtherFossilFuel	103100000	USD
CY2011Q4	us-gaap	Energy Related Inventory Other Fossil Fuel EnergyRelatedInventoryOtherFossilFuel	101900000	USD
CY2011	us-gaap	Equity Method Investment Dividends Or Distributions EquityMethodInvestmentDividendsOrDistributions	32300000	USD
CY2010	us-gaap	Equity Method Investment Dividends Or Distributions EquityMethodInvestmentDividendsOrDistributions	32200000	USD
CY2012	us-gaap	Equity Method Investment Dividends Or Distributions EquityMethodInvestmentDividendsOrDistributions	34200000	USD
CY2011Q4	us-gaap	Equity Method Investment Summarized Financial Information Current Assets EquityMethodInvestmentSummarizedFinancialInformationCurrentAssets	62000000	USD
CY2012Q4	us-gaap	Equity Method Investment Summarized Financial Information Current Assets EquityMethodInvestmentSummarizedFinancialInformationCurrentAssets	67000000	USD
CY2012Q4	us-gaap	Equity Method Investment Summarized Financial Information Current Liabilities EquityMethodInvestmentSummarizedFinancialInformationCurrentLiabilities	252000000	USD
CY2011Q4	us-gaap	Equity Method Investment Summarized Financial Information Current Liabilities EquityMethodInvestmentSummarizedFinancialInformationCurrentLiabilities	299000000	USD
CY2010	us-gaap	Equity Method Investment Summarized Financial Information Gross Profit Loss EquityMethodInvestmentSummarizedFinancialInformationGrossProfitLoss	307000000	USD
CY2012	us-gaap	Equity Method Investment Summarized Financial Information Gross Profit Loss EquityMethodInvestmentSummarizedFinancialInformationGrossProfitLoss	326000000	USD
CY2011	us-gaap	Equity Method Investment Summarized Financial Information Gross Profit Loss EquityMethodInvestmentSummarizedFinancialInformationGrossProfitLoss	307000000	USD
CY2011	us-gaap	Equity Method Investment Summarized Financial Information Net Income Loss EquityMethodInvestmentSummarizedFinancialInformationNetIncomeLoss	218000000	USD
CY2012	us-gaap	Equity Method Investment Summarized Financial Information Net Income Loss EquityMethodInvestmentSummarizedFinancialInformationNetIncomeLoss	234000000	USD
CY2010	us-gaap	Equity Method Investment Summarized Financial Information Net Income Loss EquityMethodInvestmentSummarizedFinancialInformationNetIncomeLoss	226000000	USD
CY2012Q4	us-gaap	Equity Method Investment Summarized Financial Information Noncurrent Assets EquityMethodInvestmentSummarizedFinancialInformationNoncurrentAssets	3321000000	USD
CY2011Q4	us-gaap	Equity Method Investment Summarized Financial Information Noncurrent Assets EquityMethodInvestmentSummarizedFinancialInformationNoncurrentAssets	3100000000	USD
CY2011Q4	us-gaap	Equity Method Investment Summarized Financial Information Noncurrent Liabilities EquityMethodInvestmentSummarizedFinancialInformationNoncurrentLiabilities	1490000000	USD
CY2012Q4	us-gaap	Equity Method Investment Summarized Financial Information Noncurrent Liabilities EquityMethodInvestmentSummarizedFinancialInformationNoncurrentLiabilities	1652000000	USD
CY2011	us-gaap	Equity Method Investment Summarized Financial Information Revenue EquityMethodInvestmentSummarizedFinancialInformationRevenue	575000000	USD
CY2012	us-gaap	Equity Method Investment Summarized Financial Information Revenue EquityMethodInvestmentSummarizedFinancialInformationRevenue	611000000	USD
CY2010	us-gaap	Equity Method Investment Summarized Financial Information Revenue EquityMethodInvestmentSummarizedFinancialInformationRevenue	564000000	USD
CY2011Q4	us-gaap	Equity Method Investments EquityMethodInvestments	249600000	USD
CY2010Q4	us-gaap	Equity Method Investments EquityMethodInvestments	238500000	USD
CY2012Q4	us-gaap	Equity Method Investments EquityMethodInvestments	266600000	USD
CY2012	us-gaap	Gas Domestic Regulated Revenue GasDomesticRegulatedRevenue	396300000	USD
CY2010	us-gaap	Gas Domestic Regulated Revenue GasDomesticRegulatedRevenue	480600000	USD
CY2011	us-gaap	Gas Domestic Regulated Revenue GasDomesticRegulatedRevenue	476700000	USD
CY2012	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	324900000	USD
CY2011	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	323100000	USD
CY2010	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	291500000	USD
CY2011Q3	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	136900000	USD
CY2012Q2	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	65500000	USD
CY2011Q4	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	63900000	USD
CY2012Q1	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	39300000	USD
CY2011Q2	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	50300000	USD
CY2012Q3	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	149000000	USD
CY2012Q4	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	71100000	USD
CY2011Q1	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	72000000	USD
CY2010	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	457900000	USD
CY2011	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	410600000	USD
CY2012	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	430200000	USD
CY2010	us-gaap	Income Loss From Continuing Operations Including Portion Attributable To Noncontrolling Interest IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest	310200000	USD
CY2011	us-gaap	Income Loss From Continuing Operations Including Portion Attributable To Noncontrolling Interest IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest	341400000	USD
CY2012	us-gaap	Income Loss From Continuing Operations Including Portion Attributable To Noncontrolling Interest IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest	340800000	USD
CY2010	us-gaap	Income Loss From Continuing Operations Per Basic And Diluted Share IncomeLossFromContinuingOperationsPerBasicAndDilutedShare	2.64
CY2012	us-gaap	Income Loss From Continuing Operations Per Basic And Diluted Share IncomeLossFromContinuingOperationsPerBasicAndDilutedShare	2.93
CY2011	us-gaap	Income Loss From Continuing Operations Per Basic And Diluted Share IncomeLossFromContinuingOperationsPerBasicAndDilutedShare	2.92
CY2011Q3	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	1.23
CY2012Q4	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	0.64
CY2011Q4	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	0.58
CY2012Q1	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	0.36
CY2011Q2	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	0.45
CY2011Q1	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	0.65
CY2012Q2	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	0.60
CY2012Q3	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	1.34
CY2010	us-gaap	Income Loss From Discontinued Operations Net Of Tax IncomeLossFromDiscontinuedOperationsNetOfTax	-3900000	USD
CY2012	us-gaap	Income Loss From Discontinued Operations Net Of Tax IncomeLossFromDiscontinuedOperationsNetOfTax	-5100000	USD
CY2011	us-gaap	Income Loss From Discontinued Operations Net Of Tax IncomeLossFromDiscontinuedOperationsNetOfTax	-19500000	USD
CY2012	us-gaap	Income Loss From Discontinued Operations Net Of Tax Attributable To Reporting Entity IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity	-5100000	USD
CY2011	us-gaap	Income Loss From Discontinued Operations Net Of Tax Attributable To Reporting Entity IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity	-19500000	USD
CY2010	us-gaap	Income Loss From Discontinued Operations Net Of Tax Attributable To Reporting Entity IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity	-3900000	USD
CY2011Q4	us-gaap	Income Loss From Discontinued Operations Net Of Tax Attributable To Reporting Entity IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity	-6900000	USD
CY2011Q3	us-gaap	Income Loss From Discontinued Operations Net Of Tax Attributable To Reporting Entity IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity	-14900000	USD
CY2012Q1	us-gaap	Income Loss From Discontinued Operations Net Of Tax Attributable To Reporting Entity IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity	-4400000	USD
CY2012Q3	us-gaap	Income Loss From Discontinued Operations Net Of Tax Attributable To Reporting Entity IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity	1700000	USD
CY2012Q2	us-gaap	Income Loss From Discontinued Operations Net Of Tax Attributable To Reporting Entity IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity	400000	USD
CY2011Q2	us-gaap	Income Loss From Discontinued Operations Net Of Tax Attributable To Reporting Entity IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity	800000	USD
CY2011Q1	us-gaap	Income Loss From Discontinued Operations Net Of Tax Attributable To Reporting Entity IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity	1500000	USD
CY2012Q4	us-gaap	Income Loss From Discontinued Operations Net Of Tax Attributable To Reporting Entity IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity	-2800000	USD
CY2012	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Basic And Diluted Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicAndDilutedShare	-0.04
CY2011	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Basic And Diluted Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicAndDilutedShare	-0.18
CY2010	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Basic And Diluted Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicAndDilutedShare	-0.04
CY2011Q3	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Diluted Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare	-0.13
CY2012Q4	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Diluted Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare	-0.02
CY2012Q2	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Diluted Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare	0.00
CY2011Q2	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Diluted Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare	0.01
CY2012Q3	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Diluted Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare	0.02
CY2011Q1	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Diluted Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare	0.01
CY2012Q1	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Diluted Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare	-0.04
CY2011Q4	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Diluted Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare	-0.07
CY2012	us-gaap	Income Loss From Equity Method Investments IncomeLossFromEquityMethodInvestments	41300000	USD
CY2010	us-gaap	Income Loss From Equity Method Investments IncomeLossFromEquityMethodInvestments	38100000	USD
CY2011	us-gaap	Income Loss From Equity Method Investments IncomeLossFromEquityMethodInvestments	39300000	USD
CY2011	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	69200000	USD
CY2010	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	147700000	USD
CY2012	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	89400000	USD
CY2011	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	-10800000	USD
CY2012	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	-20300000	USD
CY2010	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	-116200000	USD
CY2012Q4	us-gaap	Income Taxes Receivable IncomeTaxesReceivable	18200000	USD
CY2011Q4	us-gaap	Income Taxes Receivable IncomeTaxesReceivable	39100000	USD
CY2011	us-gaap	Increase Decrease In Accounts Receivable IncreaseDecreaseInAccountsReceivable	54300000	USD
CY2012	us-gaap	Increase Decrease In Accounts Receivable IncreaseDecreaseInAccountsReceivable	-61300000	USD
CY2010	us-gaap	Increase Decrease In Accounts Receivable IncreaseDecreaseInAccountsReceivable	-16300000	USD
CY2010	us-gaap	Increase Decrease In Derivative Liabilities IncreaseDecreaseInDerivativeLiabilities	-52000000	USD
CY2012	us-gaap	Increase Decrease In Derivative Liabilities IncreaseDecreaseInDerivativeLiabilities	-37600000	USD
CY2012	us-gaap	Increase Decrease In Income Taxes Receivable IncreaseDecreaseInIncomeTaxesReceivable	-20900000	USD
CY2012	us-gaap	Increase Decrease In Allowance For Equity Funds Used During Construction IncreaseDecreaseInAllowanceForEquityFundsUsedDuringConstruction	14100000	USD
CY2010	us-gaap	Increase Decrease In Allowance For Equity Funds Used During Construction IncreaseDecreaseInAllowanceForEquityFundsUsedDuringConstruction	11200000	USD
CY2011	us-gaap	Increase Decrease In Allowance For Equity Funds Used During Construction IncreaseDecreaseInAllowanceForEquityFundsUsedDuringConstruction	7600000	USD
CY2011	us-gaap	Increase Decrease In Derivative Liabilities IncreaseDecreaseInDerivativeLiabilities	10700000	USD
CY2010	us-gaap	Increase Decrease In Income Taxes Receivable IncreaseDecreaseInIncomeTaxesReceivable	-130400000	USD
CY2011	us-gaap	Increase Decrease In Income Taxes Receivable IncreaseDecreaseInIncomeTaxesReceivable	-300000	USD
CY2011	us-gaap	Increase Decrease In Other Operating Capital Net IncreaseDecreaseInOtherOperatingCapitalNet	-45600000	USD
CY2012	us-gaap	Increase Decrease In Other Operating Capital Net IncreaseDecreaseInOtherOperatingCapitalNet	14200000	USD
CY2010	us-gaap	Increase Decrease In Other Operating Capital Net IncreaseDecreaseInOtherOperatingCapitalNet	-12200000	USD
CY2010	us-gaap	Increase Decrease In Other Receivables IncreaseDecreaseInOtherReceivables	-65000000	USD
CY2011	us-gaap	Increase Decrease In Other Receivables IncreaseDecreaseInOtherReceivables	-75000000	USD
CY2012	us-gaap	Increase Decrease In Other Receivables IncreaseDecreaseInOtherReceivables	10000000	USD
CY2012	us-gaap	Increase Decrease In Other Regulatory Assets IncreaseDecreaseInOtherRegulatoryAssets	178100000	USD
CY2011	us-gaap	Increase Decrease In Other Regulatory Assets IncreaseDecreaseInOtherRegulatoryAssets	413100000	USD
CY2010	us-gaap	Increase Decrease In Other Regulatory Assets IncreaseDecreaseInOtherRegulatoryAssets	20800000	USD
CY2010	us-gaap	Increase Decrease In Pension And Postretirement Obligations IncreaseDecreaseInPensionAndPostretirementObligations	-20100000	USD
CY2011	us-gaap	Increase Decrease In Pension And Postretirement Obligations IncreaseDecreaseInPensionAndPostretirementObligations	8900000	USD
CY2012	us-gaap	Increase Decrease In Pension And Postretirement Obligations IncreaseDecreaseInPensionAndPostretirementObligations	51300000	USD
CY2012	us-gaap	Increase Decrease In Regulatory Liabilities IncreaseDecreaseInRegulatoryLiabilities	16400000	USD
CY2011	us-gaap	Increase Decrease In Regulatory Liabilities IncreaseDecreaseInRegulatoryLiabilities	168300000	USD
CY2010	us-gaap	Increase Decrease In Regulatory Liabilities IncreaseDecreaseInRegulatoryLiabilities	8400000	USD
CY2012	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	15000	shares
CY2011	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	52000	shares
CY2010	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	79000	shares
CY2012	us-gaap	Interest Expense InterestExpense	156700000	USD
CY2010	us-gaap	Interest Expense InterestExpense	162800000	USD
CY2011	us-gaap	Interest Expense InterestExpense	158300000	USD
CY2011	us-gaap	Interest Paid Net InterestPaidNet	157600000	USD
CY2012	us-gaap	Interest Paid Net InterestPaidNet	155200000	USD
CY2010	us-gaap	Interest Paid Net InterestPaidNet	165500000	USD
CY2011Q4	us-gaap	Interest Payable Current InterestPayableCurrent	46600000	USD
CY2012Q4	us-gaap	Interest Payable Current InterestPayableCurrent	48000000	USD
CY2011Q4	us-gaap	Inventory Raw Materials And Supplies InventoryRawMaterialsAndSupplies	58500000	USD
CY2012Q4	us-gaap	Inventory Raw Materials And Supplies InventoryRawMaterialsAndSupplies	63100000	USD
CY2011	us-gaap	Investment Tax Credit InvestmentTaxCredit	-1800000	USD
CY2012	us-gaap	Investment Tax Credit InvestmentTaxCredit	-1700000	USD
CY2010	us-gaap	Investment Tax Credit InvestmentTaxCredit	-1800000	USD
CY2012Q4	us-gaap	Jointly Owned Utility Plant Gross Ownership Amount Of Plant In Service JointlyOwnedUtilityPlantGrossOwnershipAmountOfPlantInService	769200000	USD
CY2012Q4	us-gaap	Jointly Owned Utility Plant Ownership Amount Of Construction Work In Progress JointlyOwnedUtilityPlantOwnershipAmountOfConstructionWorkInProgress	289800000	USD
CY2012Q4	us-gaap	Jointly Owned Utility Plant Ownership Amount Of Plant Accumulated Depreciation JointlyOwnedUtilityPlantOwnershipAmountOfPlantAccumulatedDepreciation	452000000	USD
CY2011Q4	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	9687900000	USD
CY2012Q4	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	10785500000	USD
CY2012Q4	us-gaap	Liabilities Current LiabilitiesCurrent	1020000000	USD
CY2011Q4	us-gaap	Liabilities Current LiabilitiesCurrent	855200000	USD
CY2012Q4	us-gaap	Liabilities Of Assets Held For Sale LiabilitiesOfAssetsHeldForSale	31400000	USD
CY2011Q4	us-gaap	Liabilities Of Assets Held For Sale LiabilitiesOfAssetsHeldForSale	62100000	USD
CY2012Q4	us-gaap	Liabilities Of Disposal Group Including Discontinued Operation Current LiabilitiesOfDisposalGroupIncludingDiscontinuedOperationCurrent	31400000	USD
CY2011Q4	us-gaap	Liabilities Of Disposal Group Including Discontinued Operation Current LiabilitiesOfDisposalGroupIncludingDiscontinuedOperationCurrent	62000000	USD
CY2012Q4	us-gaap	Line Of Credit Facility Current Borrowing Capacity LineOfCreditFacilityCurrentBorrowingCapacity	1000000000	USD
CY2011Q4	us-gaap	Line Of Credit Facility Remaining Borrowing Capacity LineOfCreditFacilityRemainingBorrowingCapacity	897200000	USD
CY2012Q4	us-gaap	Line Of Credit Facility Remaining Borrowing Capacity LineOfCreditFacilityRemainingBorrowingCapacity	732500000	USD
CY2011Q4	us-gaap	Long Term Debt LongTermDebt	2716300000	USD
CY2012Q4	us-gaap	Long Term Debt LongTermDebt	3149900000	USD
CY2012Q4	us-gaap	Long Term Debt Current LongTermDebtCurrent	1500000	USD
CY2011Q4	us-gaap	Long Term Debt Current LongTermDebtCurrent	1400000	USD
CY2012Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Next Twelve Months LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths	51000000	USD
CY2012Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Five LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive	4000000	USD
CY2012Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Four LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour	3000000	USD
CY2012Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Three LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree	183000000	USD
CY2012Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Two LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo	358000000	USD
CY2012Q4	us-gaap	Long Term Debt Noncurrent LongTermDebtNoncurrent	3136600000	USD
CY2011Q4	us-gaap	Long Term Debt Noncurrent LongTermDebtNoncurrent	2703100000	USD
CY2012Q4	us-gaap	Long Term Investments LongTermInvestments	319000000	USD
CY2011Q4	us-gaap	Long Term Investments LongTermInvestments	300700000	USD
CY2012	us-gaap	Long Term Purchase Commitment Amount LongTermPurchaseCommitmentAmount	982000000	USD
CY2011Q4	us-gaap	Minority Interest MinorityInterest	1800000	USD
CY2012Q4	us-gaap	Minority Interest MinorityInterest	1800000	USD
CY2011	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-198500000	USD
CY2012	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	324200000	USD
CY2010	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-134400000	USD
CY2010	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-866500000	USD
CY2012	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-1155500000	USD
CY2011	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-652100000	USD
CY2012	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	841100000	USD
CY2011	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	702700000	USD
CY2010	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	984900000	USD
CY2011	us-gaap	Net Income Loss NetIncomeLoss	321900000	USD
CY2010	us-gaap	Net Income Loss NetIncomeLoss	306300000	USD
CY2012	us-gaap	Net Income Loss NetIncomeLoss	335700000	USD
CY2011	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	303600000	USD
CY2012	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	319800000	USD
CY2010	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	287600000	USD
CY2011Q2	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	51100000	USD
CY2011Q1	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	73500000	USD
CY2012Q4	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	68300000	USD
CY2011Q4	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	57000000	USD
CY2011Q3	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	122000000	USD
CY2012Q3	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	150700000	USD
CY2012Q1	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	34900000	USD
CY2012Q2	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	65900000	USD
CY2010	us-gaap	Nonoperating Income Expense NonoperatingIncomeExpense	-102100000	USD
CY2012	us-gaap	Nonoperating Income Expense NonoperatingIncomeExpense	-89500000	USD
CY2011	us-gaap	Nonoperating Income Expense NonoperatingIncomeExpense	-102700000	USD
CY2012Q4	us-gaap	Notes And Loans Receivable Net Current NotesAndLoansReceivableNetCurrent	14900000	USD
CY2011Q4	us-gaap	Notes And Loans Receivable Net Current NotesAndLoansReceivableNetCurrent	22200000	USD
CY2011Q4	us-gaap	Notes And Loans Receivable Net Noncurrent NotesAndLoansReceivableNetNoncurrent	28200000	USD
CY2012Q4	us-gaap	Notes And Loans Receivable Net Noncurrent NotesAndLoansReceivableNetNoncurrent	13000000	USD
CY2011Q4	us-gaap	Notes Receivable Net NotesReceivableNet	50400000	USD
CY2012Q4	us-gaap	Notes Receivable Net NotesReceivableNet	27900000	USD
CY2010	us-gaap	Operating Income Loss OperatingIncomeLoss	560000000	USD
CY2011	us-gaap	Operating Income Loss OperatingIncomeLoss	513300000	USD
CY2012	us-gaap	Operating Income Loss OperatingIncomeLoss	519700000	USD
CY2011Q4	us-gaap	Operating Income Loss OperatingIncomeLoss	106000000	USD
CY2012Q4	us-gaap	Operating Income Loss OperatingIncomeLoss	101600000	USD
CY2011Q2	us-gaap	Operating Income Loss OperatingIncomeLoss	70600000	USD
CY2011Q1	us-gaap	Operating Income Loss OperatingIncomeLoss	127300000	USD
CY2012Q2	us-gaap	Operating Income Loss OperatingIncomeLoss	108800000	USD
CY2011Q3	us-gaap	Operating Income Loss OperatingIncomeLoss	209400000	USD
CY2012Q1	us-gaap	Operating Income Loss OperatingIncomeLoss	95600000	USD
CY2012Q3	us-gaap	Operating Income Loss OperatingIncomeLoss	213700000	USD
CY2012Q4	us-gaap	Operating Leases Future Minimum Payments Due OperatingLeasesFutureMinimumPaymentsDue	56000000	USD
CY2012Q4	us-gaap	Operating Leases Future Minimum Payments Due Current OperatingLeasesFutureMinimumPaymentsDueCurrent	9000000	USD
CY2012Q4	us-gaap	Operating Leases Future Minimum Payments Due In Five Years OperatingLeasesFutureMinimumPaymentsDueInFiveYears	2000000	USD
CY2012Q4	us-gaap	Operating Leases Future Minimum Payments Due In Four Years OperatingLeasesFutureMinimumPaymentsDueInFourYears	3000000	USD
CY2012Q4	us-gaap	Operating Leases Future Minimum Payments Due In Three Years OperatingLeasesFutureMinimumPaymentsDueInThreeYears	5000000	USD
CY2012Q4	us-gaap	Operating Leases Future Minimum Payments Due In Two Years OperatingLeasesFutureMinimumPaymentsDueInTwoYears	13000000	USD
CY2012Q4	us-gaap	Operating Leases Future Minimum Payments Due Thereafter OperatingLeasesFutureMinimumPaymentsDueThereafter	24000000	USD
CY2011	us-gaap	Operating Leases Rent Expense Contingent Rentals OperatingLeasesRentExpenseContingentRentals	5000000	USD
CY2010	us-gaap	Operating Leases Rent Expense Contingent Rentals OperatingLeasesRentExpenseContingentRentals	5000000	USD
CY2012	us-gaap	Operating Leases Rent Expense Contingent Rentals OperatingLeasesRentExpenseContingentRentals	6000000	USD
CY2012	us-gaap	Operating Leases Rent Expense Minimum Rentals OperatingLeasesRentExpenseMinimumRentals	69000000	USD
CY2011	us-gaap	Operating Leases Rent Expense Minimum Rentals OperatingLeasesRentExpenseMinimumRentals	70000000	USD
CY2010	us-gaap	Operating Leases Rent Expense Minimum Rentals OperatingLeasesRentExpenseMinimumRentals	70000000	USD
CY2011	us-gaap	Operating Leases Rent Expense Net OperatingLeasesRentExpenseNet	75000000	USD
CY2010	us-gaap	Operating Leases Rent Expense Net OperatingLeasesRentExpenseNet	75000000	USD
CY2012	us-gaap	Operating Leases Rent Expense Net OperatingLeasesRentExpenseNet	75000000	USD
CY2011	us-gaap	Other Amortization Of Deferred Charges OtherAmortizationOfDeferredCharges	56300000	USD
CY2010	us-gaap	Other Amortization Of Deferred Charges OtherAmortizationOfDeferredCharges	51800000	USD
CY2012	us-gaap	Other Amortization Of Deferred Charges OtherAmortizationOfDeferredCharges	55000000	USD
CY2011Q4	us-gaap	Other Assets Current OtherAssetsCurrent	37700000	USD
CY2012Q4	us-gaap	Other Assets Current OtherAssetsCurrent	43300000	USD
CY2011Q4	us-gaap	Other Assets Noncurrent OtherAssetsNoncurrent	91900000	USD
CY2012Q4	us-gaap	Other Assets Noncurrent OtherAssetsNoncurrent	105300000	USD
CY2011	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	600000	USD
CY2010	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	0	USD
CY2012	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	0	USD
CY2011	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	600000	USD
CY2010	us-gaap	Other Cost And Expense Operating OtherCostAndExpenseOperating	19400000	USD
CY2012	us-gaap	Other Cost And Expense Operating OtherCostAndExpenseOperating	11900000	USD
CY2011	us-gaap	Other Cost And Expense Operating OtherCostAndExpenseOperating	18000000	USD
CY2011Q4	us-gaap	Other Liabilities Current OtherLiabilitiesCurrent	107000000	USD
CY2012Q4	us-gaap	Other Liabilities Current OtherLiabilitiesCurrent	113500000	USD
CY2011Q4	us-gaap	Other Liabilities Noncurrent OtherLiabilitiesNoncurrent	259400000	USD
CY2012Q4	us-gaap	Other Liabilities Noncurrent OtherLiabilitiesNoncurrent	262500000	USD
CY2011	us-gaap	Other Noncash Income Expense OtherNoncashIncomeExpense	5200000	USD
CY2012	us-gaap	Other Noncash Income Expense OtherNoncashIncomeExpense	2600000	USD
CY2010	us-gaap	Other Noncash Income Expense OtherNoncashIncomeExpense	4700000	USD
CY2011	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	4300000	USD
CY2010	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	4600000	USD
CY2012	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	4000000	USD
CY2012Q4	us-gaap	Other Receivables OtherReceivables	209400000	USD
CY2011Q4	us-gaap	Other Receivables OtherReceivables	114900000	USD
CY2012	us-gaap	Other Sales Revenue Net OtherSalesRevenueNet	56700000	USD
CY2010	us-gaap	Other Sales Revenue Net OtherSalesRevenueNet	64600000	USD
CY2011	us-gaap	Other Sales Revenue Net OtherSalesRevenueNet	62000000	USD
CY2011	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	4600000	USD
CY2012	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	19900000	USD
CY2010	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	16700000	USD
CY2010	us-gaap	Payments For Repurchase Of Redeemable Preferred Stock PaymentsForRepurchaseOfRedeemablePreferredStock	0	USD
CY2012	us-gaap	Payments For Repurchase Of Redeemable Preferred Stock PaymentsForRepurchaseOfRedeemablePreferredStock	0	USD
CY2011	us-gaap	Payments For Repurchase Of Redeemable Preferred Stock PaymentsForRepurchaseOfRedeemablePreferredStock	40000000	USD
CY2010	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	174600000	USD
CY2012	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	199300000	USD
CY2011	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	188100000	USD
CY2011	us-gaap	Payments Of Dividends Preferred Stock And Preference Stock PaymentsOfDividendsPreferredStockAndPreferenceStock	16800000	USD
CY2012	us-gaap	Payments Of Dividends Preferred Stock And Preference Stock PaymentsOfDividendsPreferredStockAndPreferenceStock	15900000	USD
CY2010	us-gaap	Payments Of Dividends Preferred Stock And Preference Stock PaymentsOfDividendsPreferredStockAndPreferenceStock	18700000	USD
CY2011	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	673400000	USD
CY2010	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	866900000	USD
CY2012	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	1158100000	USD
CY2011Q4	us-gaap	Pension And Other Postretirement Defined Benefit Plans Liabilities Noncurrent PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent	312700000	USD
CY2012Q4	us-gaap	Pension And Other Postretirement Defined Benefit Plans Liabilities Noncurrent PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent	364000000	USD
CY2011Q4	us-gaap	Preferred Stock Value PreferredStockValue	145100000	USD
CY2012Q4	us-gaap	Preferred Stock Value PreferredStockValue	145100000	USD
CY2012Q4	us-gaap	Prepaid Taxes PrepaidTaxes	40400000	USD
CY2011Q4	us-gaap	Prepaid Taxes PrepaidTaxes	40200000	USD
CY2012	us-gaap	Prior Period Reclassification Adjustment Description PriorPeriodReclassificationAdjustmentDescription	<div style="font-family:Times New Roman;font-size:10pt;"><div style="line-height:120%;text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">Certain prior period amounts in the Consolidated Financial Statements and Notes to Consolidated Financial Statements have been reclassified to conform to the current period presentation for comparative purposes. Unless otherwise noted, the notes herein have been revised to exclude discontinued operations and assets and liabilities held for sale for all periods presented.</font></div></div>
CY2010	us-gaap	Proceeds From Issuance Of Long Term Debt ProceedsFromIssuanceOfLongTermDebt	500000000	USD
CY2011	us-gaap	Proceeds From Issuance Of Long Term Debt ProceedsFromIssuanceOfLongTermDebt	400000	USD
CY2012	us-gaap	Proceeds From Issuance Of Long Term Debt ProceedsFromIssuanceOfLongTermDebt	385000000	USD
CY2010	us-gaap	Proceeds From Payments For Other Financing Activities ProceedsFromPaymentsForOtherFinancingActivities	9300000	USD
CY2011	us-gaap	Proceeds From Payments For Other Financing Activities ProceedsFromPaymentsForOtherFinancingActivities	-8100000	USD
CY2012	us-gaap	Proceeds From Payments For Other Financing Activities ProceedsFromPaymentsForOtherFinancingActivities	-8900000	USD
CY2012	us-gaap	Proceeds From Repayments Of Short Term Debt ProceedsFromRepaymentsOfShortTermDebt	164700000	USD
CY2011	us-gaap	Proceeds From Repayments Of Short Term Debt ProceedsFromRepaymentsOfShortTermDebt	55400000	USD
CY2010	us-gaap	Proceeds From Repayments Of Short Term Debt ProceedsFromRepaymentsOfShortTermDebt	-142600000	USD
CY2011	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	2500000	USD
CY2012	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	900000	USD
CY2010	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	5500000	USD
CY2012Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	7838000000	USD
CY2011Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	7033300000	USD
CY2012Q4	us-gaap	Property Plant And Equipment Other PropertyPlantAndEquipmentOther	455700000	USD
CY2011Q4	us-gaap	Property Plant And Equipment Other PropertyPlantAndEquipmentOther	418800000	USD
CY2012	us-gaap	Provision For Doubtful Accounts ProvisionForDoubtfulAccounts	4000000	USD
CY2011	us-gaap	Provision For Doubtful Accounts ProvisionForDoubtfulAccounts	4200000	USD
CY2011Q4	us-gaap	Public Utilities Property Plant And Equipment Net PublicUtilitiesPropertyPlantAndEquipmentNet	6614500000	USD
CY2012Q4	us-gaap	Public Utilities Property Plant And Equipment Other Property Plant And Equipment PublicUtilitiesPropertyPlantAndEquipmentOtherPropertyPlantAndEquipment	21200000	USD
CY2011Q4	us-gaap	Public Utilities Property Plant And Equipment Accumulated Depreciation PublicUtilitiesPropertyPlantAndEquipmentAccumulatedDepreciation	3206000000	USD
CY2012Q4	us-gaap	Public Utilities Property Plant And Equipment Accumulated Depreciation PublicUtilitiesPropertyPlantAndEquipmentAccumulatedDepreciation	3513000000	USD
CY2012Q4	us-gaap	Public Utilities Property Plant And Equipment Net PublicUtilitiesPropertyPlantAndEquipmentNet	7382300000	USD
CY2012	us-gaap	Public Utilities Allowance For Funds Used During Construction Additions PublicUtilitiesAllowanceForFundsUsedDuringConstructionAdditions	21900000	USD
CY2010	us-gaap	Public Utilities Allowance For Funds Used During Construction Additions PublicUtilitiesAllowanceForFundsUsedDuringConstructionAdditions	18000000	USD
CY2011	us-gaap	Public Utilities Allowance For Funds Used During Construction Additions PublicUtilitiesAllowanceForFundsUsedDuringConstructionAdditions	12000000	USD
CY2011Q4	us-gaap	Public Utilities Property Plant And Equipment Other Property Plant And Equipment PublicUtilitiesPropertyPlantAndEquipmentOtherPropertyPlantAndEquipment	34900000	USD
CY2011Q4	us-gaap	Regulatory Assets RegulatoryAssets	1495000000	USD
CY2012Q4	us-gaap	Regulatory Assets RegulatoryAssets	1612400000	USD
CY2012Q4	us-gaap	Regulatory Assets Current RegulatoryAssetsCurrent	83500000	USD
CY2011Q4	us-gaap	Regulatory Assets Current RegulatoryAssetsCurrent	103600000	USD
CY2011Q4	us-gaap	Regulatory Assets Noncurrent RegulatoryAssetsNoncurrent	1391400000	USD
CY2012Q4	us-gaap	Regulatory Assets Noncurrent RegulatoryAssetsNoncurrent	1528900000	USD
CY2012Q4	us-gaap	Regulatory Liabilities RegulatoryLiabilities	916100000	USD
CY2011Q4	us-gaap	Regulatory Liabilities RegulatoryLiabilities	910100000	USD
CY2011Q4	us-gaap	Regulatory Liability Current RegulatoryLiabilityCurrent	164700000	USD
CY2012Q4	us-gaap	Regulatory Liability Current RegulatoryLiabilityCurrent	189700000	USD
CY2012Q4	us-gaap	Regulatory Liability Noncurrent RegulatoryLiabilityNoncurrent	726400000	USD
CY2011Q4	us-gaap	Regulatory Liability Noncurrent RegulatoryLiabilityNoncurrent	745400000	USD
CY2010	us-gaap	Repayments Of Long Term Debt RepaymentsOfLongTermDebt	307800000	USD
CY2012	us-gaap	Repayments Of Long Term Debt RepaymentsOfLongTermDebt	1400000	USD
CY2011	us-gaap	Repayments Of Long Term Debt RepaymentsOfLongTermDebt	1300000	USD
CY2012Q4	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	1630700000	USD
CY2011Q4	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	1510200000	USD
CY2010	us-gaap	Revenues Revenues	3262100000	USD
CY2012	us-gaap	Revenues Revenues	3094500000	USD
CY2011	us-gaap	Revenues Revenues	3221400000	USD
CY2011Q4	us-gaap	Revenues Revenues	760800000	USD
CY2012Q1	us-gaap	Revenues Revenues	765700000	USD
CY2011Q2	us-gaap	Revenues Revenues	712500000	USD
CY2012Q2	us-gaap	Revenues Revenues	690300000	USD
CY2012Q4	us-gaap	Revenues Revenues	750900000	USD
CY2011Q3	us-gaap	Revenues Revenues	870900000	USD
CY2011Q1	us-gaap	Revenues Revenues	877200000	USD
CY2012Q3	us-gaap	Revenues Revenues	887600000	USD
CY2011Q4	us-gaap	Sales Revenue Goods Net Percentage SalesRevenueGoodsNetPercentage	1.00
CY2012Q4	us-gaap	Sales Revenue Goods Net Percentage SalesRevenueGoodsNetPercentage	1.00
CY2010Q4	us-gaap	Sales Revenue Goods Net Percentage SalesRevenueGoodsNetPercentage	1.00
CY2010	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Exercises In Period Total Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue	1100000	USD
CY2011	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Exercises In Period Total Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue	1600000	USD
CY2012	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Exercises In Period Total Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue	800000	USD
CY2012Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue	500000	USD
CY2012	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Outstanding Weighted Average Remaining Contractual Term2 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2	P1Y
CY2011Q4	us-gaap	Short Term Debt Weighted Average Interest Rate ShortTermDebtWeightedAverageInterestRate	0.003
CY2012Q4	us-gaap	Short Term Debt Weighted Average Interest Rate ShortTermDebtWeightedAverageInterestRate	0.004
CY2012	us-gaap	Shortterm Debt Average Outstanding Amount ShorttermDebtAverageOutstandingAmount	99800000	USD
CY2011	us-gaap	Shortterm Debt Average Outstanding Amount ShorttermDebtAverageOutstandingAmount	27700000	USD
CY2012	us-gaap	Shortterm Debt Maximum Amount Outstanding During Period ShorttermDebtMaximumAmountOutstandingDuringPeriod	217500000	USD
CY2011	us-gaap	Shortterm Debt Maximum Amount Outstanding During Period ShorttermDebtMaximumAmountOutstandingDuringPeriod	124400000	USD
CY2011	us-gaap	Stock Issued During Period Shares Employee Stock Purchase Plans StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans	164400	shares
CY2010	us-gaap	Stock Issued During Period Shares Employee Stock Purchase Plans StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans	260316	shares
CY2012	us-gaap	Stock Issued During Period Shares Employee Stock Purchase Plans StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans	20195	shares
CY2011Q4	us-gaap	Stockholders Equity StockholdersEquity	3013000000	USD
CY2012Q4	us-gaap	Stockholders Equity StockholdersEquity	3134900000	USD
CY2009Q4	us-gaap	Stockholders Equity StockholdersEquity	2772600000	USD
CY2010Q4	us-gaap	Stockholders Equity StockholdersEquity	2893600000	USD
CY2012Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	3281800000	USD
CY2011Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	3159900000	USD
CY2011	us-gaap	Tax Benefit From Stock Options Exercised1 TaxBenefitFromStockOptionsExercised1	700000	USD
CY2010	us-gaap	Tax Benefit From Stock Options Exercised1 TaxBenefitFromStockOptionsExercised1	400000	USD
CY2012	us-gaap	Tax Benefit From Stock Options Exercised1 TaxBenefitFromStockOptionsExercised1	300000	USD
CY2011	us-gaap	Taxes Excluding Income And Excise Taxes TaxesExcludingIncomeAndExciseTaxes	98200000	USD
CY2010	us-gaap	Taxes Excluding Income And Excise Taxes TaxesExcludingIncomeAndExciseTaxes	95800000	USD
CY2012	us-gaap	Taxes Excluding Income And Excise Taxes TaxesExcludingIncomeAndExciseTaxes	98200000	USD
CY2012Q4	us-gaap	Taxes Payable Current TaxesPayableCurrent	48000000	USD
CY2011Q4	us-gaap	Taxes Payable Current TaxesPayableCurrent	46900000	USD
CY2012Q4	us-gaap	Temporary Equity Carrying Amount Attributable To Parent TemporaryEquityCarryingAmountAttributableToParent	60000000	USD
CY2011Q4	us-gaap	Temporary Equity Carrying Amount Attributable To Parent TemporaryEquityCarryingAmountAttributableToParent	60000000	USD
CY2011Q4	us-gaap	Unamortized Debt Issuance Expense UnamortizedDebtIssuanceExpense	19100000	USD
CY2012Q4	us-gaap	Unamortized Debt Issuance Expense UnamortizedDebtIssuanceExpense	19500000	USD
CY2009Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	101700000	USD
CY2011Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	23500000	USD
CY2012Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	700000	USD
CY2010Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	66700000	USD
CY2010	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions	-31800000	USD
CY2011	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions	-43900000	USD
CY2012	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions	-23500000	USD
CY2010	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Settlements With Taxing Authorities UnrecognizedTaxBenefitsDecreasesResultingFromSettlementsWithTaxingAuthorities	-16100000	USD
CY2012	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Settlements With Taxing Authorities UnrecognizedTaxBenefitsDecreasesResultingFromSettlementsWithTaxingAuthorities	0	USD
CY2011	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Settlements With Taxing Authorities UnrecognizedTaxBenefitsDecreasesResultingFromSettlementsWithTaxingAuthorities	0	USD
CY2011	us-gaap	Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions	700000	USD
CY2010	us-gaap	Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions	3800000	USD
CY2012	us-gaap	Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions	700000	USD
CY2011	us-gaap	Unrecognized Tax Benefits Increases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions	0	USD
CY2012	us-gaap	Unrecognized Tax Benefits Increases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions	0	USD
CY2010	us-gaap	Unrecognized Tax Benefits Increases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions	9100000	USD
CY2012Q4	us-gaap	Unrecognized Tax Benefits Interest On Income Taxes Accrued UnrecognizedTaxBenefitsInterestOnIncomeTaxesAccrued	0	USD
CY2011Q4	us-gaap	Unrecognized Tax Benefits Interest On Income Taxes Accrued UnrecognizedTaxBenefitsInterestOnIncomeTaxesAccrued	400000	USD
CY2010Q4	us-gaap	Unrecognized Tax Benefits Interest On Income Taxes Accrued UnrecognizedTaxBenefitsInterestOnIncomeTaxesAccrued	700000	USD
CY2012Q4	us-gaap	Unrecognized Tax Benefits That Would Impact Effective Tax Rate UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate	700000	USD
CY2011Q4	us-gaap	Unrecognized Tax Benefits That Would Impact Effective Tax Rate UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate	0	USD
CY2010Q4	us-gaap	Unrecognized Tax Benefits That Would Impact Effective Tax Rate UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate	0	USD
CY2010	us-gaap	Unregulated Operating Revenue UnregulatedOperatingRevenue	42700000	USD
CY2011	us-gaap	Unregulated Operating Revenue UnregulatedOperatingRevenue	46900000	USD
CY2012	us-gaap	Unregulated Operating Revenue UnregulatedOperatingRevenue	52200000	USD
CY2012	us-gaap	Use Of Estimates UseOfEstimates	<div style="font-family:Times New Roman;font-size:10pt;"><div style="line-height:120%;text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;font-weight:bold;text-decoration:underline;">Use of Estimates</font><font style="font-family:inherit;font-size:10pt;"> - The preparation of the consolidated financial statements requires management to make estimates and assumptions that affect: (a) the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the financial statements; and (b) the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.</font></div></div>
CY2011	us-gaap	Utilities Operating Expense Maintenance And Operations UtilitiesOperatingExpenseMaintenanceAndOperations	630200000	USD
CY2012	us-gaap	Utilities Operating Expense Maintenance And Operations UtilitiesOperatingExpenseMaintenanceAndOperations	590000000	USD
CY2010	us-gaap	Utilities Operating Expense Maintenance And Operations UtilitiesOperatingExpenseMaintenanceAndOperations	617200000	USD
CY2010	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	110521000	shares
CY2011	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	110678000	shares
CY2012	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	110768000	shares
CY2011	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	110626000	shares
CY2010	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	110442000	shares
CY2012	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	110753000	shares
CY2012Q4	lnt	Accumulated Depreciation On Property Plant And Equipment Non Regulated Business Line1 AccumulatedDepreciationOnPropertyPlantAndEquipmentNonRegulatedBusinessLine1	31000000	USD
CY2011Q4	lnt	Accumulated Depreciation On Property Plant And Equipment Non Regulated Business Line1 AccumulatedDepreciationOnPropertyPlantAndEquipmentNonRegulatedBusinessLine1	26400000	USD
CY2012Q4	lnt	Accumulated Depreciation On Property Plant And Equipment Non Regulated Business Line2 AccumulatedDepreciationOnPropertyPlantAndEquipmentNonRegulatedBusinessLine2	200200000	USD
CY2011Q4	lnt	Accumulated Depreciation On Property Plant And Equipment Non Regulated Business Line2 AccumulatedDepreciationOnPropertyPlantAndEquipmentNonRegulatedBusinessLine2	177400000	USD
CY2011Q4	lnt	Accumulated Depreciation On Public Utilities Property Plant And Equipment Other Property Plant And Equipment AccumulatedDepreciationOnPublicUtilitiesPropertyPlantAndEquipmentOtherPropertyPlantAndEquipment	5300000	USD
CY2012Q4	lnt	Accumulated Depreciation On Public Utilities Property Plant And Equipment Other Property Plant And Equipment AccumulatedDepreciationOnPublicUtilitiesPropertyPlantAndEquipmentOtherPropertyPlantAndEquipment	5600000	USD
CY2010	lnt	Adjustment Depreciation And Amortization Including Discontinued Operations AdjustmentDepreciationAndAmortizationIncludingDiscontinuedOperations	292300000	USD
CY2012	lnt	Adjustment Depreciation And Amortization Including Discontinued Operations AdjustmentDepreciationAndAmortizationIncludingDiscontinuedOperations	332900000	USD
CY2011	lnt	Adjustment Depreciation And Amortization Including Discontinued Operations AdjustmentDepreciationAndAmortizationIncludingDiscontinuedOperations	323800000	USD
CY2012	lnt	Advances For Customer Energy Efficiency Projects AdvancesForCustomerEnergyEfficiencyProjects	400000	USD
CY2010	lnt	Advances For Customer Energy Efficiency Projects AdvancesForCustomerEnergyEfficiencyProjects	17100000	USD
CY2011	lnt	Advances For Customer Energy Efficiency Projects AdvancesForCustomerEnergyEfficiencyProjects	5100000	USD
CY2012	lnt	Amount Acquired To Exercise Shareowner Rights Agreement AmountAcquiredToExerciseShareownerRightsAgreement	0.15
CY2012	lnt	Capital Leases Lease Term CapitalLeasesLeaseTerm	P20Y
CY2012	lnt	Carrying Value Of Entity Deferred Compensation Obligations Interest And Equity Accounts CarryingValueOfEntityDeferredCompensationObligationsInterestAndEquityAccounts	16300000	USD
CY2011	lnt	Carrying Value Of Entity Deferred Compensation Obligations Interest And Equity Accounts CarryingValueOfEntityDeferredCompensationObligationsInterestAndEquityAccounts	20500000	USD
CY2012Q4	lnt	Class Of Warrant Or Right Exercise Price Of Warrant Or Right Percentage Of Exercise Price Upon Change In Beneficial Ownership ClassOfWarrantOrRightExercisePriceOfWarrantOrRightPercentageOfExercisePriceUponChangeInBeneficialOwnership	2
CY2012Q4	lnt	Class Of Warrant Or Right Initial Right Entitlement Number Of Shares Of Common Stock Shareholders Have Option To Purchase ClassOfWarrantOrRightInitialRightEntitlementNumberOfSharesOfCommonStockShareholdersHaveOptionToPurchase	0.5	shares
CY2011	lnt	Collections Of Advances For Customer Energy Efficiency Projects CollectionsOfAdvancesForCustomerEnergyEfficiencyProjects	31000000	USD
CY2012	lnt	Collections Of Advances For Customer Energy Efficiency Projects CollectionsOfAdvancesForCustomerEnergyEfficiencyProjects	22900000	USD
CY2010	lnt	Collections Of Advances For Customer Energy Efficiency Projects CollectionsOfAdvancesForCustomerEnergyEfficiencyProjects	34200000	USD
CY2011Q4	lnt	Common Stock Held In Trust Shares CommonStockHeldInTrustShares	262735	shares
CY2012Q4	lnt	Common Stock Held In Trust Shares CommonStockHeldInTrustShares	216030	shares
CY2011Q4	lnt	Common Stock Held In Trust Weighted Average Value Per Share CommonStockHeldInTrustWeightedAverageValuePerShare	31.68
CY2012Q4	lnt	Common Stock Held In Trust Weighted Average Value Per Share CommonStockHeldInTrustWeightedAverageValuePerShare	33.61
CY2011Q4	lnt	Common Stock Percentage In Assets Held Saving Plans CommonStockPercentageInAssetsHeldSavingPlans	0.146
CY2012Q4	lnt	Common Stock Percentage In Assets Held Saving Plans CommonStockPercentageInAssetsHeldSavingPlans	0.125
CY2012Q4	lnt	Construction Work In Progress Business Line4 ConstructionWorkInProgressBusinessLine4	130400000	USD
CY2011Q4	lnt	Construction Work In Progress Business Line4 ConstructionWorkInProgressBusinessLine4	9000000	USD
CY2012Q4	lnt	Construction Work In Progress Business Line5 ConstructionWorkInProgressBusinessLine5	66900000	USD
CY2011Q4	lnt	Construction Work In Progress Business Line5 ConstructionWorkInProgressBusinessLine5	8300000	USD
CY2011Q4	lnt	Construction Work In Progress Business Line6 ConstructionWorkInProgressBusinessLine6	7700000	USD
CY2012Q4	lnt	Construction Work In Progress Business Line6 ConstructionWorkInProgressBusinessLine6	73700000	USD
CY2012Q4	lnt	Construction Work In Progress Other ConstructionWorkInProgressOther	147800000	USD
CY2011Q4	lnt	Construction Work In Progress Other ConstructionWorkInProgressOther	232200000	USD
CY2010	lnt	Cost Electric Production Fuel And Energy Purchases CostElectricProductionFuelAndEnergyPurchases	819200000	USD
CY2012	lnt	Cost Electric Production Fuel And Energy Purchases CostElectricProductionFuelAndEnergyPurchases	712300000	USD
CY2011	lnt	Cost Electric Production Fuel And Energy Purchases CostElectricProductionFuelAndEnergyPurchases	764500000	USD
CY2012	lnt	Cost Of Gas Sold CostOfGasSold	217200000	USD
CY2011	lnt	Cost Of Gas Sold CostOfGasSold	295200000	USD
CY2010	lnt	Cost Of Gas Sold CostOfGasSold	304000000	USD
CY2012	lnt	Cost Purchased Electric Capacity CostPurchasedElectricCapacity	271500000	USD
CY2010	lnt	Cost Purchased Electric Capacity CostPurchasedElectricCapacity	279700000	USD
CY2011	lnt	Cost Purchased Electric Capacity CostPurchasedElectricCapacity	257200000	USD
CY2012Q4	lnt	Debt To Capital Ratios Actual Status DebtToCapitalRatiosActualStatus	0.50
CY2012Q4	lnt	Deferred Charges Regulatory Assets And Other Assets Noncurrent DeferredChargesRegulatoryAssetsAndOtherAssetsNoncurrent	1634200000	USD
CY2011Q4	lnt	Deferred Charges Regulatory Assets And Other Assets Noncurrent DeferredChargesRegulatoryAssetsAndOtherAssetsNoncurrent	1483300000	USD
CY2012	lnt	Deferred Compensation Plan Base Salary And Incentive Compensation Percentage DeferredCompensationPlanBaseSalaryAndIncentiveCompensationPercentage	1
CY2012Q4	lnt	Defined Benefit Pension And Other Postretirement Benefits Plans Total Plan Assets Percentage On Common Stock DefinedBenefitPensionAndOtherPostretirementBenefitsPlansTotalPlanAssetsPercentageOnCommonStock	0.01
CY2011Q4	lnt	Defined Benefit Pension And Other Postretirement Benefits Plans Total Plan Assets Percentage On Common Stock DefinedBenefitPensionAndOtherPostretirementBenefitsPlansTotalPlanAssetsPercentageOnCommonStock	0.01
CY2012Q4	lnt	Defined Benefit Plan Plan Asset Threshold For Long Term Allocation Targets DefinedBenefitPlanPlanAssetThresholdForLongTermAllocationTargets	5000000	USD
CY2012	lnt	Defined Benefit Plan Postreitrement Health Care Plan Minimum Age Of Participants Covered DefinedBenefitPlanPostreitrementHealthCarePlanMinimumAgeOfParticipantsCovered	P65Y
CY2012Q4	lnt	Defined Benefit Plan Regulatory Liability Before Tax DefinedBenefitPlanRegulatoryLiabilityBeforeTax	2700000	USD
CY2011Q4	lnt	Defined Benefit Plan Regulatory Liability Before Tax DefinedBenefitPlanRegulatoryLiabilityBeforeTax	3300000	USD
CY2012	lnt	Disposal Group Including Discontinued Operation Interest Expense And Other DisposalGroupIncludingDiscontinuedOperationInterestExpenseAndOther	700000	USD
CY2011	lnt	Disposal Group Including Discontinued Operation Interest Expense And Other DisposalGroupIncludingDiscontinuedOperationInterestExpenseAndOther	0	USD
CY2010	lnt	Disposal Group Including Discontinued Operation Interest Expense And Other DisposalGroupIncludingDiscontinuedOperationInterestExpenseAndOther	1000000	USD
CY2010	lnt	Effective Income Tax Rate Reconciliation Effect Of Rate Making On Property Related Differences EffectiveIncomeTaxRateReconciliationEffectOfRateMakingOnPropertyRelatedDifferences	-0.042
CY2012	lnt	Effective Income Tax Rate Reconciliation Effect Of Rate Making On Property Related Differences EffectiveIncomeTaxRateReconciliationEffectOfRateMakingOnPropertyRelatedDifferences	-0.050
CY2011	lnt	Effective Income Tax Rate Reconciliation Effect Of Rate Making On Property Related Differences EffectiveIncomeTaxRateReconciliationEffectOfRateMakingOnPropertyRelatedDifferences	-0.020
CY2011Q4	lnt	Fair Value Of Deferred Proceeds Of Receivables Sold FairValueOfDeferredProceedsOfReceivablesSold	53700000	USD
CY2012Q4	lnt	Fair Value Of Deferred Proceeds Of Receivables Sold FairValueOfDeferredProceedsOfReceivablesSold	66800000	USD
CY2012	lnt	Gain On Sale Of Assets Percent Recognized During Each Year Of Deferral Period GainOnSaleOfAssetsPercentRecognizedDuringEachYearOfDeferralPeriod	0.125
CY2012Q4	lnt	Hybrid Securities Maximum Limit HybridSecuritiesMaximumLimit	0.15
CY2011	lnt	Increase Decrease In Income And Other Taxes Payable Noncurrent IncreaseDecreaseInIncomeAndOtherTaxesPayableNoncurrent	-5100000	USD
CY2012	lnt	Increase Decrease In Income And Other Taxes Payable Noncurrent IncreaseDecreaseInIncomeAndOtherTaxesPayableNoncurrent	-2900000	USD
CY2010	lnt	Increase Decrease In Income And Other Taxes Payable Noncurrent IncreaseDecreaseInIncomeAndOtherTaxesPayableNoncurrent	-66600000	USD
CY2012Q4	lnt	Individual Commitments Incurred IndividualCommitmentsIncurred	1000000	USD
CY2011	lnt	Interest Expense Net Of Allowance For Funds Used During Construction InterestExpenseNetOfAllowanceForFundsUsedDuringConstruction	146300000	USD
CY2010	lnt	Interest Expense Net Of Allowance For Funds Used During Construction InterestExpenseNetOfAllowanceForFundsUsedDuringConstruction	144800000	USD
CY2012	lnt	Interest Expense Net Of Allowance For Funds Used During Construction InterestExpenseNetOfAllowanceForFundsUsedDuringConstruction	134800000	USD
CY2012Q4	lnt	Investments Business Line1 InvestmentsBusinessLine1	257000000	USD
CY2011Q4	lnt	Investments Business Line1 InvestmentsBusinessLine1	238800000	USD
CY2012Q4	lnt	Jointly Owned Utility Cost Of Removal Obligations Included In Regulatory Liabilities JointlyOwnedUtilityCostOfRemovalObligationsIncludedInRegulatoryLiabilities	44500000	USD
CY2012	lnt	Long Term Debt Weighted Average Remaining Maturity LongTermDebtWeightedAverageRemainingMaturity	P8D
CY2012Q3	lnt	Loss Contingency Number Of New Subclasses Certified As Result Of Court Opinion And Order LossContingencyNumberOfNewSubclassesCertifiedAsResultOfCourtOpinionAndOrder	2	subclass
CY2009	lnt	Minimum Rating Of Amendment In Participants Interest Credit MinimumRatingOfAmendmentInParticipantsInterestCredit	0.03
CY2012Q4	lnt	Net Utility Plant NetUtilityPlant	6942300000	USD
CY2011Q4	lnt	Net Utility Plant NetUtilityPlant	6322400000	USD
CY2012	lnt	Non Cash Valuation Charges NonCashValuationCharges	3300000	USD
CY2011	lnt	Non Cash Valuation Charges NonCashValuationCharges	25500000	USD
CY2010	lnt	Non Cash Valuation Charges NonCashValuationCharges	38000000	USD
CY2012Q4	lnt	Number Of Short Term Debt Instruments Revolving Credit Facilities NumberOfShortTermDebtInstrumentsRevolvingCreditFacilities	3	revolving_credit_facility
CY2011	lnt	Other Common Stock Activity OtherCommonStockActivity	39480	shares
CY2012	lnt	Other Common Stock Activity OtherCommonStockActivity	51616	shares
CY2010	lnt	Other Common Stock Activity OtherCommonStockActivity	22913	shares
CY2012Q4	lnt	Other Long Term Investments And Marketable Securities OtherLongTermInvestmentsAndMarketableSecurities	62000000	USD
CY2011Q4	lnt	Other Long Term Investments And Marketable Securities OtherLongTermInvestmentsAndMarketableSecurities	61900000	USD
CY2012	lnt	Payments To Acquire Productive Assets Business Line1 PaymentsToAcquireProductiveAssetsBusinessLine1	403500000	USD
CY2010	lnt	Payments To Acquire Productive Assets Business Line1 PaymentsToAcquireProductiveAssetsBusinessLine1	0	USD
CY2011	lnt	Payments To Acquire Productive Assets Business Line1 PaymentsToAcquireProductiveAssetsBusinessLine1	0	USD
CY2011	lnt	Payments To Acquire Productive Assets Business Line2 PaymentsToAcquireProductiveAssetsBusinessLine2	65300000	USD
CY2010	lnt	Payments To Acquire Productive Assets Business Line2 PaymentsToAcquireProductiveAssetsBusinessLine2	33600000	USD
CY2012	lnt	Payments To Acquire Productive Assets Business Line2 PaymentsToAcquireProductiveAssetsBusinessLine2	132600000	USD
CY2010	lnt	Payments To Acquire Productive Assets Other PaymentsToAcquireProductiveAssetsOther	833300000	USD
CY2012	lnt	Payments To Acquire Productive Assets Other PaymentsToAcquireProductiveAssetsOther	622000000	USD
CY2011	lnt	Payments To Acquire Productive Assets Other PaymentsToAcquireProductiveAssetsOther	608100000	USD
CY2012Q4	lnt	Performance Guarantees Outstanding PerformanceGuaranteesOutstanding	615000000	USD
CY2012Q4	lnt	Present Value Abandonment Obligation PresentValueAbandonmentObligation	30000000	USD
CY2012	lnt	Production Tax Credits Net Of State Tax Impacts ProductionTaxCreditsNetOfStateTaxImpacts	24800000	USD
CY2010	lnt	Production Tax Credits Net Of State Tax Impacts ProductionTaxCreditsNetOfStateTaxImpacts	11200000	USD
CY2011	lnt	Production Tax Credits Net Of State Tax Impacts ProductionTaxCreditsNetOfStateTaxImpacts	27100000	USD
CY2012Q4	lnt	Property Plant And Equipment Nonregulated Business Line1 PropertyPlantAndEquipmentNonregulatedBusinessLine1	258600000	USD
CY2011Q4	lnt	Property Plant And Equipment Nonregulated Business Line1 PropertyPlantAndEquipmentNonregulatedBusinessLine1	270600000	USD
CY2011Q4	lnt	Property Plant And Equipment Nonregulated Business Line2 PropertyPlantAndEquipmentNonregulatedBusinessLine2	148200000	USD
CY2012Q4	lnt	Property Plant And Equipment Nonregulated Business Line2 PropertyPlantAndEquipmentNonregulatedBusinessLine2	197100000	USD
CY2012	lnt	Provision Recorded As Change In Accrued Interest ProvisionRecordedAsChangeInAccruedInterest	-200000	USD
CY2010	lnt	Provision Recorded As Change In Accrued Interest ProvisionRecordedAsChangeInAccruedInterest	-3000000	USD
CY2011	lnt	Provision Recorded As Change In Accrued Interest ProvisionRecordedAsChangeInAccruedInterest	-500000	USD
CY2012	lnt	Provision Recorded As Change In Uncertain Tax Positions Current ProvisionRecordedAsChangeInUncertainTaxPositionsCurrent	8000000	USD
CY2010	lnt	Provision Recorded As Change In Uncertain Tax Positions Current ProvisionRecordedAsChangeInUncertainTaxPositionsCurrent	-84000000	USD
CY2011	lnt	Provision Recorded As Change In Uncertain Tax Positions Current ProvisionRecordedAsChangeInUncertainTaxPositionsCurrent	16300000	USD
CY2010	lnt	Provision Recorded As Change In Uncertain Tax Positions Deferred ProvisionRecordedAsChangeInUncertainTaxPositionsDeferred	59600000	USD
CY2012	lnt	Provision Recorded As Change In Uncertain Tax Positions Deferred ProvisionRecordedAsChangeInUncertainTaxPositionsDeferred	-7600000	USD
CY2011	lnt	Provision Recorded As Change In Uncertain Tax Positions Deferred ProvisionRecordedAsChangeInUncertainTaxPositionsDeferred	-38300000	USD
CY2010	lnt	Public Utilities Contingent Agreement Electric Base Rate Case Not To Be Filed Period PublicUtilitiesContingentAgreementElectricBaseRateCaseNotToBeFiledPeriod	P3Y
CY2012Q4	lnt	Public Utilities Property Plant And Equipment Electric PublicUtilitiesPropertyPlantAndEquipmentElectric	9070700000	USD
CY2011Q4	lnt	Public Utilities Property Plant And Equipment Electric PublicUtilitiesPropertyPlantAndEquipmentElectric	8165400000	USD
CY2011Q4	lnt	Public Utilities Property Plant And Equipment Gas PublicUtilitiesPropertyPlantAndEquipmentGas	852900000	USD
CY2012Q4	lnt	Public Utilities Property Plant And Equipment Gas PublicUtilitiesPropertyPlantAndEquipmentGas	878400000	USD
CY2011Q4	lnt	Public Utilities Property Plant And Equipment General PublicUtilitiesPropertyPlantAndEquipmentGeneral	510100000	USD
CY2012Q4	lnt	Public Utilities Property Plant And Equipment General PublicUtilitiesPropertyPlantAndEquipmentGeneral	506200000	USD
CY2009	lnt	Purchase Of Development Rights PurchaseOfDevelopmentRights	100	MW
CY2012Q4	lnt	Shares Available For Issuance Pursuant To Various Plans SharesAvailableForIssuancePursuantToVariousPlans	8400000	shares
CY2012	lnt	Short Term Debt Weighted Average Remaining Maturity ShortTermDebtWeightedAverageRemainingMaturity	P11D
CY2011	lnt	Short Term Debt Weighted Average Remaining Maturity ShortTermDebtWeightedAverageRemainingMaturity	P3D
CY2012	lnt	Stock Issued During Period Value Repurchase And Other Net StockIssuedDuringPeriodValueRepurchaseAndOtherNet	1400000	USD
CY2011	lnt	Stock Issued During Period Value Repurchase And Other Net StockIssuedDuringPeriodValueRepurchaseAndOtherNet	3300000	USD
CY2010	lnt	Stock Issued During Period Value Repurchase And Other Net StockIssuedDuringPeriodValueRepurchaseAndOtherNet	8000000	USD
CY2012Q4	lnt	Temporary Equity And Preferred Stock Fair Value TemporaryEquityAndPreferredStockFairValue	212600000	USD
CY2012Q4	lnt	Total Deferred Credits And Other Liabilities TotalDeferredCreditsAndOtherLiabilities	3287100000	USD
CY2011Q4	lnt	Total Deferred Credits And Other Liabilities TotalDeferredCreditsAndOtherLiabilities	2909700000	USD
CY2011	lnt	Weighted Average Interest Rate Short Term Debt WeightedAverageInterestRateShortTermDebt	0.003
CY2012	lnt	Weighted Average Interest Rate Short Term Debt WeightedAverageInterestRateShortTermDebt	0.004
CY2012Q4	lnt	Wind Projects Generating Production Tax Credits WindProjectsGeneratingProductionTaxCredits	3	wind_projects
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	0000352541
CY2013Q1	dei	Entity Common Stock Shares Outstanding EntityCommonStockSharesOutstanding	110990924	shares
CY2012	dei	Entity Current Reporting Status EntityCurrentReportingStatus	Yes
CY2012	dei	Entity Filer Category EntityFilerCategory	Large Accelerated Filer
CY2012Q2	dei	Entity Public Float EntityPublicFloat	5000000000	USD
CY2012	dei	Entity Registrant Name EntityRegistrantName	ALLIANT ENERGY CORP
CY2012	dei	Entity Voluntary Filers EntityVoluntaryFilers	No
CY2012	dei	Entity Well Known Seasoned Issuer EntityWellKnownSeasonedIssuer	Yes

Files In Submission

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$LNT
ALLIANT ENERGY CORP Stock $lnt

2012 Form 10-K Financial Statement

#000035254113000007 Filed on February 26, 2013

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$LNT ALLIANT ENERGY CORP Stock $lnt

2012 Form 10-K Financial Statement

#000035254113000007 Filed on February 26, 2013

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$LNT
ALLIANT ENERGY CORP Stock $lnt