XML 67 R48.htm IDEA: XBRL DOCUMENT
v3.5.0.2

Investments (Narrative) (Details) $ in Millions | 6 Months Ended
--- | ---
Jun. 30, 2016 USD ($)
Schedule of Investments [Line Items] |
Proceeds from liquidation of company-owned life insurance policies | $ 31
IPL [Member] |
Schedule of Investments [Line Items] |
Proceeds from liquidation of company-owned life insurance policies | $ 19

X
- Definition Line items represent reporting concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 12 -Section 12 -Sentence Column A + Details
Name: | invest_InvestmentLineItems
Namespace Prefix: | invest_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The net cash outflow or inflow for net proceeds and payments derived from carrying life insurance policies for which the entity is the beneficiary. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Investing Activities -URI http://asc.fasb.org/extlink&oid=6516133 + Details
Name: | us-gaap_PaymentsForProceedsFromLifeInsurancePolicies
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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