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v2.4.1.9

Segments Of Business (Narrative) (Details) | 12 Months Ended
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Dec. 31, 2014 segment
IPL and WPL [Member] |
Segment Reporting Information [Line Items] |
Number of reportable segments (in segments) | 3 us-gaap_NumberOfReportableSegments / dei_LegalEntityAxis = lnt_IplAndWplMember
IPL [Member] |
Segment Reporting Information [Line Items] |
Number of reportable segments (in segments) | 3 us-gaap_NumberOfReportableSegments / dei_LegalEntityAxis = lnt_IplMember
WPL [Member] |
Segment Reporting Information [Line Items] |
Number of reportable segments (in segments) | 3 us-gaap_NumberOfReportableSegments / dei_LegalEntityAxis = lnt_WplMember

X
- Definition Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements. + References No definition available. + Details
Name: | us-gaap_NumberOfReportableSegments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

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

X
- Details
Name: | dei_LegalEntityAxis=lnt_IplAndWplMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=lnt_IplMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=lnt_WplMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |