XML 48 R77.htm IDEA: XBRL DOCUMENT
v3.19.3.a.u2

Debt (Schedule Of Debt-To-Capital Ratios) (Details) | Dec. 31, 2019
--- | ---
Actual debt-to-capital ratio | 55.00%
IPL [Member] |
Actual debt-to-capital ratio | 48.00%
WPL [Member] |
Actual debt-to-capital ratio | 48.00%
Maximum [Member] |
Requirement, not to exceed | 65.00%
Maximum [Member] | IPL [Member] |
Requirement, not to exceed | 65.00%
Maximum [Member] | WPL [Member] |
Requirement, not to exceed | 65.00%

X
- Definition Debt to capital ratios actual status + References No definition available. + Details
Name: | lnt_DebtToCapitalRatiosActualStatus
Namespace Prefix: | lnt_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Debt to capital ratios base percentage + References No definition available. + Details
Name: | lnt_DebtToCapitalRatiosBasePercentage
Namespace Prefix: | lnt_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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: |

X
- Details
Name: | srt_RangeAxis=srt_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |