XML 72 R51.htm IDEA: XBRL DOCUMENT
v3.10.0.1

Revenues Revenue (Disaggregation of Revenues) (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2018 | Sep. 30, 2017 | Sep. 30, 2018 | Sep. 30, 2017
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | $ 928.6 | $ 906.9 | $ 2,661.0 | $ 2,526.1
Electric [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 861.2 | 840.6 | 2,296.2 | 2,199.1
Electric [Member] | Retail - residential [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 312.9 | 296.4 | 820.6 | 766.9
Electric [Member] | Retail - commercial [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 215.4 | 205.9 | 561.7 | 537.3
Electric [Member] | Retail - industrial [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 247.8 | 243.4 | 675.1 | 646.2
Electric [Member] | Wholesale [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 50.0 | 63.5 | 146.9 | 186.3
Electric [Member] | Other [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 35.1 | 31.4 | 91.9 | 62.4
Gas [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 44.8 | 45.8 | 299.0 | 262.7
Gas [Member] | Retail - residential [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 21.8 | 21.5 | 170.1 | 145.1
Gas [Member] | Retail - commercial [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 11.0 | 12.9 | 87.3 | 81.4
Gas [Member] | Retail - industrial [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 3.0 | 3.0 | 11.4 | 10.4
Gas [Member] | Other [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 9.0 | 8.4 | 30.2 | 25.8
Other Utility [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 12.3 | 11.2 | 36.2 | 34.4
Other Utility [Member] | Steam [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 8.7 | 8.3 | 26.5 | 25.3
Other Utility [Member] | Other [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 3.6 | 2.9 | 9.7 | 9.1
Non-utility and Other [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 10.3 | 9.3 | 29.6 | 29.9
Non-utility and Other [Member] | Transportation and other [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 10.3 | 9.3 | 29.6 | 29.9
IPL [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 547.6 | 527.4 | 1,548.2 | 1,398.1
IPL [Member] | Electric [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 509.2 | 489.0 | 1,337.0 | 1,217.6
IPL [Member] | Electric [Member] | Retail - residential [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 180.1 | 168.5 | 461.6 | 414.2
IPL [Member] | Electric [Member] | Retail - commercial [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 146.0 | 137.5 | 371.8 | 340.6
IPL [Member] | Electric [Member] | Retail - industrial [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 141.4 | 137.3 | 385.0 | 350.7
IPL [Member] | Electric [Member] | Wholesale [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 18.2 | 26.7 | 56.4 | 71.3
IPL [Member] | Electric [Member] | Other [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 23.5 | 19.0 | 62.2 | 40.8
IPL [Member] | Gas [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 26.7 | 27.4 | 177.0 | 147.2
IPL [Member] | Gas [Member] | Retail - residential [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 12.6 | 12.0 | 100.9 | 78.7
IPL [Member] | Gas [Member] | Retail - commercial [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 6.4 | 7.8 | 49.8 | 44.4
IPL [Member] | Gas [Member] | Retail - industrial [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 2.0 | 2.2 | 6.1 | 6.8
IPL [Member] | Gas [Member] | Other [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 5.7 | 5.4 | 20.2 | 17.3
IPL [Member] | Other Utility [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 11.7 | 11.0 | 34.2 | 33.3
IPL [Member] | Other Utility [Member] | Steam [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 8.7 | 8.3 | 26.5 | 25.3
IPL [Member] | Other Utility [Member] | Other [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 3.0 | 2.7 | 7.7 | 8.0
WPL [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 370.7 | 370.2 | 1,083.2 | 1,098.1
WPL [Member] | Electric [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 352.0 | 351.6 | 959.2 | 981.5
WPL [Member] | Electric [Member] | Retail - residential [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 132.8 | 127.9 | 359.0 | 352.7
WPL [Member] | Electric [Member] | Retail - commercial [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 69.4 | 68.4 | 189.9 | 196.7
WPL [Member] | Electric [Member] | Retail - industrial [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 106.4 | 106.1 | 290.1 | 295.5
WPL [Member] | Electric [Member] | Wholesale [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 31.8 | 36.8 | 90.5 | 115.0
WPL [Member] | Electric [Member] | Other [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 11.6 | 12.4 | 29.7 | 21.6
WPL [Member] | Gas [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 18.1 | 18.4 | 122.0 | 115.5
WPL [Member] | Gas [Member] | Retail - residential [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 9.2 | 9.5 | 69.2 | 66.4
WPL [Member] | Gas [Member] | Retail - commercial [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 4.6 | 5.1 | 37.5 | 37.0
WPL [Member] | Gas [Member] | Retail - industrial [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 1.0 | 0.8 | 5.3 | 3.6
WPL [Member] | Gas [Member] | Other [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 3.3 | 3.0 | 10.0 | 8.5
WPL [Member] | Other Utility [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 0.6 | 0.2 | 2.0 | 1.1
WPL [Member] | Other Utility [Member] | Other [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | $ 0.6 | $ 0.2 | $ 2.0 | $ 1.1

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_DisaggregationOfRevenueLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 32 -Paragraph 2A -URI http://asc.fasb.org/extlink&oid=82859839&loc=SL82860478-203043 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 50 -Paragraph 4 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=82913847&loc=SL49130543-203045 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=82913847&loc=SL49130539-203045 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=82913847&loc=SL49130545-203045 + Details
Name: | us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=lnt_ElectricMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_MajorCustomersAxis=lnt_RetailResidentialMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_MajorCustomersAxis=lnt_RetailCommercialMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_MajorCustomersAxis=lnt_RetailIndustrialMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_MajorCustomersAxis=lnt_WholesaleMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_MajorCustomersAxis=lnt_OtherCustomerMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=lnt_GasMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=lnt_OtherUtilityMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_MajorCustomersAxis=lnt_SteamMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=us-gaap_AllOtherSegmentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_MajorCustomersAxis=lnt_TransportationandOtherMember
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: |