XML 94 R71.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Related Parties (Service Agreements) (Details) - Corporate Services [Member] - Subsidiary of Common Parent [Member] - USD ($) $ in Millions | 3 Months Ended
--- | ---
Mar. 31, 2018 | Mar. 31, 2017
Administrative and General Services Billings [Member] | IPL [Member] |  |
Related Party Transactions [Line Items] |  |
Amounts billed between related parties | $ 41 | $ 39
Administrative and General Services Billings [Member] | WPL [Member] |  |
Related Party Transactions [Line Items] |  |
Amounts billed between related parties | 33 | 31
Sales Credited [Member] | IPL [Member] |  |
Related Party Transactions [Line Items] |  |
Amounts billed between related parties | 5 | 2
Sales Credited [Member] | WPL [Member] |  |
Related Party Transactions [Line Items] |  |
Amounts billed between related parties | 1 | 0
Purchases Billed [Member] | IPL [Member] |  |
Related Party Transactions [Line Items] |  |
Amounts billed between related parties | 93 | 66
Purchases Billed [Member] | WPL [Member] |  |
Related Party Transactions [Line Items] |  |
Amounts billed between related parties | $ 17 | $ 34

X
- Definition Amount of transactions with related party during the financial reporting period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 850 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39603-107864 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 850 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 850 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39622-107864 + Details
Name: | us-gaap_RelatedPartyTransactionAmountsOfTransaction
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Line items represent financial 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 No definition available. + Details
Name: | us-gaap_RelatedPartyTransactionLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_RelatedPartyTransactionAxis=lnt_AdministrativeandGeneralServicesBillingsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_CounterpartyNameAxis=lnt_CorporateServicesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=us-gaap_SubsidiaryOfCommonParentMember
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: |

X
- Details
Name: | us-gaap_RelatedPartyTransactionAxis=lnt_TransmissionSalesCreditedMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RelatedPartyTransactionAxis=lnt_TransmissionPurchasesBilledMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |