XML 164 R122.htm IDEA: XBRL DOCUMENT
v3.6.0.2

Fair Value Measurements (Narrative) (Details) | 12 Months Ended
--- | ---
Dec. 31, 2016
5.1% [Member] | Redeemable Preferred Stock [Member] | IPL [Member] |
Cumulative preferred stock rate | 5.10%

X
- Definition The percentage rate used to calculate dividend payments on preferred stock. + References No definition available. + Details
Name: | us-gaap_PreferredStockDividendRatePercentage
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | lnt_RedeemablePreferredStockByDividendRateAxis=lnt_FivePointOnePercentageMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementClassOfStockAxis=us-gaap_RedeemablePreferredStockMember
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: |