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Benefit Plans (Expected Benefit Payments) (Details) $ in Millions | Dec. 31, 2015 USD ($)
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Defined Benefit Plan Disclosure [Line Items] |
Expected benefit payments, 2016 | $ 87.3
Expected benefit payments, 2017 | 92.4
Expected benefit payments, 2018 | 91.0
Expected benefit payments, 2019 | 92.6
Expected benefit payments, 2020 | 96.9
Expected benefit payments, 2021 - 2025 | 488.3
Defined Benefit Pension Plans [Member] |
Defined Benefit Plan Disclosure [Line Items] |
Expected benefit payments, 2016 | 69.5
Expected benefit payments, 2017 | 74.3
Expected benefit payments, 2018 | 72.8
Expected benefit payments, 2019 | 74.3
Expected benefit payments, 2020 | 78.7
Expected benefit payments, 2021 - 2025 | 401.4
Other Postretirement Benefits Plans [Member] |
Defined Benefit Plan Disclosure [Line Items] |
Expected benefit payments, 2016 | 17.8
Expected benefit payments, 2017 | 18.1
Expected benefit payments, 2018 | 18.2
Expected benefit payments, 2019 | 18.3
Expected benefit payments, 2020 | 18.2
Expected benefit payments, 2021 - 2025 | 86.9
IPL [Member] |
Defined Benefit Plan Disclosure [Line Items] |
Expected benefit payments, 2016 | 40.4
Expected benefit payments, 2017 | 41.7
Expected benefit payments, 2018 | 42.4
Expected benefit payments, 2019 | 42.1
Expected benefit payments, 2020 | 45.4
Expected benefit payments, 2021 - 2025 | 226.8
IPL [Member] | Defined Benefit Pension Plans [Member] |
Defined Benefit Plan Disclosure [Line Items] |
Expected benefit payments, 2016 | 32.8
Expected benefit payments, 2017 | 34.1
Expected benefit payments, 2018 | 34.8
Expected benefit payments, 2019 | 34.6
Expected benefit payments, 2020 | 37.8
Expected benefit payments, 2021 - 2025 | 190.8
IPL [Member] | Other Postretirement Benefits Plans [Member] |
Defined Benefit Plan Disclosure [Line Items] |
Expected benefit payments, 2016 | 7.6
Expected benefit payments, 2017 | 7.6
Expected benefit payments, 2018 | 7.6
Expected benefit payments, 2019 | 7.5
Expected benefit payments, 2020 | 7.6
Expected benefit payments, 2021 - 2025 | 36.0
WPL [Member] |
Defined Benefit Plan Disclosure [Line Items] |
Expected benefit payments, 2016 | 36.6
Expected benefit payments, 2017 | 37.6
Expected benefit payments, 2018 | 38.5
Expected benefit payments, 2019 | 38.9
Expected benefit payments, 2020 | 39.8
Expected benefit payments, 2021 - 2025 | 198.4
WPL [Member] | Defined Benefit Pension Plans [Member] |
Defined Benefit Plan Disclosure [Line Items] |
Expected benefit payments, 2016 | 29.1
Expected benefit payments, 2017 | 29.8
Expected benefit payments, 2018 | 30.7
Expected benefit payments, 2019 | 31.1
Expected benefit payments, 2020 | 32.2
Expected benefit payments, 2021 - 2025 | 163.7
WPL [Member] | Other Postretirement Benefits Plans [Member] |
Defined Benefit Plan Disclosure [Line Items] |
Expected benefit payments, 2016 | 7.5
Expected benefit payments, 2017 | 7.8
Expected benefit payments, 2018 | 7.8
Expected benefit payments, 2019 | 7.8
Expected benefit payments, 2020 | 7.6
Expected benefit payments, 2021 - 2025 | $ 34.7

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- Definition Amount of benefits from a defined benefit plan expected to be paid in the five fiscal years after the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (f) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920 + Details
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- Definition Amount of benefits from a defined benefit plan expected to be paid in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (f) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920 + Details
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