XML 74 R79.htm IDEA: XBRL DOCUMENT
v2.4.0.8

Commitments And Contingencies (Narrative) (Details) (USD $) In Millions, unless otherwise specified | 1 Months Ended | 9 Months Ended |  | 1 Months Ended | 9 Months Ended | 12 Months Ended | 1 Months Ended |  | 9 Months Ended
--- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Jul. 31, 2012 subclass | Dec. 31, 2010 | Sep. 30, 2013 | Sep. 30, 2013 IPL [Member] site | Sep. 30, 2013 WPL [Member] site | Sep. 30, 2013 Manufactured Gas Plant Sites [Member] | Sep. 30, 2013 Manufactured Gas Plant Sites [Member] IPL [Member] | Sep. 30, 2013 Manufactured Gas Plant Sites [Member] WPL [Member] | Sep. 30, 2013 Indemnifications [Member] RMT [Member] | Sep. 30, 2012 Defined benefit pension plans [Member] | Sep. 30, 2013 Defined benefit pension plans [Member] | Dec. 31, 2011 Defined benefit pension plans [Member] | Feb. 28, 2013 Defined benefit pension plans [Member] Cash Balance Plan [Member] | Sep. 30, 2012 Defined benefit pension plans [Member] Cash Balance Plan [Member] | Sep. 30, 2013 Performance guarantees outstanding, 2013 [Member] | Sep. 30, 2013 Performance guarantees outstanding, 2014 [Member] | Sep. 30, 2013 Performance guarantees outstanding, 2015 [Member] | Sep. 30, 2013 Scenario, Forecast [Member] | Sep. 30, 2013 Scenario, Forecast [Member] IPL [Member] | Sep. 30, 2013 Scenario, Forecast [Member] WPL [Member] | Sep. 30, 2013 Scenario, Forecast [Member] Capital Purchase Obligation [Member] | Sep. 30, 2013 Scenario, Forecast [Member] Capital Purchase Obligation [Member] IPL [Member] | Sep. 30, 2013 Scenario, Forecast [Member] Capital Purchase Obligation [Member] WPL [Member] | Sep. 30, 2013 Civil Penalty [Member] WPL [Member] | Sep. 30, 2013 Environmental Issue [Member] WPL [Member] | Sep. 30, 2013 Minimum [Member] | Sep. 30, 2013 Maximum [Member]
Long-term Purchase Commitment [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Minimum future commitments |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 2,692 | $ 2,096 | $ 592 | $ 64 | $ 21 | $ 43 |  |  |  |
Interest crediting rate |  | 8.20% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate additional payments to certain plan participants |  |  |  |  |  |  |  |  |  |  |  | 10 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of new subclasses certified as a result of court opinion and order (in subclasses) | 2 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Estimated damages from court opinion and order |  |  |  |  |  |  |  |  |  |  | 18.7 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss contingency, damages sought, value |  |  |  |  |  |  |  |  |  |  |  |  |  | 9.6 |  |  |  |  |  |  |  |  |  |  |  |  |
Damages to be paid out of common fund |  |  |  |  |  |  |  |  |  | 4.3 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss contingency, damages awarded, value |  |  |  |  |  |  |  |  |  |  |  |  | 6.4 |  |  |  |  |  |  |  |  |  |  | 2.0 | 7.0 |  |
Stautue of limitations, lump sum distributions |  |  | 6 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss contingency, estimate of possible loss |  |  |  |  |  |  |  |  | 3 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Warranty period |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 12 months | 60 months
Performance guarantees outstanding |  |  | 493 |  |  |  |  |  |  |  |  |  |  |  | 146 | 294 | 53 |  |  |  |  |  |  |  |  |  |
Present value abandonment obligation |  |  | 31 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of sites monitoring and remediating (in sites) |  |  |  | 27 | 5 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Minimum remaining estimated cost incurred for investigation, remediation and monitoring |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 15 | 13 | 2 |  |  |  |  |  |  |
Maximum remaining estimated cost incurred for investigation, remediation and monitoring |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 32 | 28 | 4 |  |  |  |  |  |  |
Current and non-current environmental liabilities |  |  |  |  |  | $ 20 | $ 17 | $ 3 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |

X
- Definition Aggregate Additional Payments To Certain Plan Participants + References No definition available. + Details
Name: | lnt_AggregateAdditionalPaymentsToCertainPlanParticipants
Namespace Prefix: | lnt_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Damages to be paid out of common fund + References No definition available. + Details
Name: | lnt_DamagesToBePaidOutOfCommonFund
Namespace Prefix: | lnt_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Interest crediting rate used to project cash balance accounts + References No definition available. + Details
Name: | lnt_InterestCreditingRate
Namespace Prefix: | lnt_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Judgment Of Damages By The Court, Maximum + References No definition available. + Details
Name: | lnt_JudgmentOfDamagesByCourtMaximum
Namespace Prefix: | lnt_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Loss Contingency, Damages Sought, Value, Amount of Plaintiff's Attorney Fees or Costs + References No definition available. + Details
Name: | lnt_LossContingencyDamagesSoughtValueAmountOfPlaintiffsAttorneyFeesOrCosts
Namespace Prefix: | lnt_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Loss Contingency, Number of New Subclasses Certified as a Result of Court Opinion and Order + References No definition available. + Details
Name: | lnt_LossContingencyNumberOfNewSubclassesCertifiedAsResultOfCourtOpinionAndOrder
Namespace Prefix: | lnt_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Maximum Remaining Estimated Cost Incurred for Investigation, Remediation and Monitoring + References No definition available. + Details
Name: | lnt_MaximumRemainingEstimatedCostIncurredForInvestigationRemediationAndMonitoring
Namespace Prefix: | lnt_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Minimum Remaining Estimated Cost Incurred for Investigation, Remediation and Monitoring + References No definition available. + Details
Name: | lnt_MinimumRemainingEstimatedCostIncurredForInvestigationRemediationAndMonitoring
Namespace Prefix: | lnt_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Number of sites remediating and monitoring + References No definition available. + Details
Name: | lnt_Numberofsitesremediatingandmonitoring
Namespace Prefix: | lnt_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Performance Guarantees Outstanding + References No definition available. + Details
Name: | lnt_PerformanceGuaranteesOutstanding
Namespace Prefix: | lnt_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Present value abandonment obligation + References No definition available. + Details
Name: | lnt_PresentValueAbandonmentObligation
Namespace Prefix: | lnt_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Stautue Of Limitations, Distributions + References No definition available. + Details
Name: | lnt_StautueOfLimitationsDistributions
Namespace Prefix: | lnt_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Warranty Period + References No definition available. + Details
Name: | lnt_WarrantyPeriod
Namespace Prefix: | lnt_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Total costs accrued as of the balance sheet date for environmental loss contingencies. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 30 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13207-110859 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Statement of Position (SOP) -Number 96-1 -Paragraph 161 -Subparagraph a -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6952336&loc=d3e14326-108349 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 25 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6395460&loc=d3e13647-108346 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 5 -Paragraph 9 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. + Details
Name: | us-gaap_AccrualForEnvironmentalLossContingencies
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The minimum amount the entity agreed to spend under the long-term purchase commitment. + References No definition available. + Details
Name: | us-gaap_LongTermPurchaseCommitmentAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | us-gaap_LongTermPurchaseCommitmentLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of damages awarded to the plaintiff in the legal matter. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6952336&loc=d3e14326-108349 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 4 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6952336&loc=d3e14435-108349 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 9 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6952336&loc=d3e14557-108349 + Details
Name: | us-gaap_LossContingencyDamagesAwardedValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Reflects the estimated amount of loss from the specified contingency as of the balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 5 -Paragraph 9, 10, 11, 12 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 4 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6952336&loc=d3e14435-108349 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 9 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6952336&loc=d3e14557-108349 + Details
Name: | us-gaap_LossContingencyEstimateOfPossibleLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant