XML 80 R80.htm IDEA: XBRL DOCUMENT
v2.4.0.8

Commitments And Contingencies Commitments And Contingencies (MPG Site Estimated Future Costs And Recorded Liabilities) (Details) (Manufactured Gas Plant Sites [Member], USD $) In Millions, unless otherwise specified | 3 Months Ended
--- | ---
Mar. 31, 2014
Long-term Purchase Commitment [Line Items] |
Minimum range of estimated future costs | $ 14
Maximum range of estimated future costs | 33
Current and non-current environmental liabilities | 21
IPL [Member] |
Long-term Purchase Commitment [Line Items] |
Minimum range of estimated future costs | 13
Maximum range of estimated future costs | 31
Current and non-current environmental liabilities | 19
WPL [Member] |
Long-term Purchase Commitment [Line Items] |
Minimum range of estimated future costs | 1
Maximum range of estimated future costs | 2
Current and non-current environmental liabilities | $ 2

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 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 FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14326-108349 Reference 3: 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 + Details
Name: | us-gaap_AccrualForEnvironmentalLossContingencies
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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