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Property, Plant and Equipment (Property, Plant and Equipment) (Details) - USD ($) $ in Millions | Dec. 31, 2018 | Dec. 31, 2017
--- | --- | ---
Property, Plant and Equipment [Line Items] |  |  |
Electric plant anticipated to be retired early | [1] | $ 0.0 | $ 93.0
Total electric plant |  | 12,663.6 | 12,296.9
Gas plant in service |  | 1,387.6 | 1,244.0
Other plant in service |  | 513.2 | 571.9
Accumulated depreciation |  | (4,314.6) | (4,283.1)
Net plant |  | 10,249.8 | 9,829.7
Construction work in progress |  | 1,774.8 | 962.2
Other, net |  | 6.1 | 6.0
Total utility |  | 12,030.7 | 10,797.9
Non-utility Generation, net | [2] | 86.9 | 90.9
Corporate Services and other, net | [3] | 344.8 | 345.7
Total non-utility and other |  | 431.7 | 436.6
Total property, plant and equipment |  | 12,462.4 | 11,234.5
Non-utility Generation, accumulated depreciation |  | 54.5 | 50.5
Corporate Services and other, accumulated depreciation |  | 167.5 | 285.6
Generation [Member] |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Electric plant in service |  | 6,800.6 | 6,655.3
Distribution [Member] |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Electric plant in service |  | 5,452.2 | 5,123.5
Other [Member] |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Electric plant in service |  | 410.8 | 425.1
IPL [Member] |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Electric plant anticipated to be retired early |  | 0.0 | 0.0
Total electric plant |  | 6,894.5 | 6,819.1
Gas plant in service |  | 763.1 | 654.8
Other plant in service |  | 322.4 | 333.4
Accumulated depreciation |  | (2,294.7) | (2,311.0)
Net plant |  | 5,685.3 | 5,496.3
Construction work in progress |  | 1,091.2 | 424.4
Other, net |  | 5.0 | 5.5
Total utility |  | 6,781.5 | 5,926.2
Total property, plant and equipment |  | 6,781.5 | 5,926.2
IPL [Member] | Generation [Member] |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Electric plant in service |  | 3,610.4 | 3,715.9
IPL [Member] | Distribution [Member] |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Electric plant in service |  | 3,023.7 | 2,820.9
IPL [Member] | Other [Member] |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Electric plant in service |  | 260.4 | 282.3
WPL [Member] |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Electric plant anticipated to be retired early | [1] | 0.0 | 93.0
Total electric plant |  | 5,769.1 | 5,477.8
Gas plant in service |  | 624.5 | 589.2
Other plant in service |  | 190.8 | 238.5
Accumulated depreciation |  | (2,019.9) | (1,972.1)
Net plant |  | 4,564.5 | 4,333.4
Leased Sheboygan Falls Energy Facility, net | [4] | 38.1 | 46.2
Construction work in progress |  | 683.6 | 537.8
Other, net |  | 1.1 | 0.5
Total utility |  | 5,287.3 | 4,917.9
Total property, plant and equipment |  | 5,287.3 | 4,917.9
Leased Sheboygan Falls Energy Facility, accumulated depreciation |  | 82.8 | 77.6
WPL [Member] | Generation [Member] |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Electric plant in service |  | 3,190.2 | 2,939.4
WPL [Member] | Distribution [Member] |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Electric plant in service |  | 2,428.5 | 2,302.6
WPL [Member] | Other [Member] |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Electric plant in service |  | $ 150.4 | $ 142.8
[1] | In 2018, WPL retired Edgewater Unit 4 and reclassified the remaining net book value of this EGU from property, plant and equipment to a regulatory asset on Alliant Energy’s and WPL’s balance sheets.
[2] | Less accumulated depreciation of $54.5 million and $50.5 million for Alliant Energy as of December 31, 2018 and 2017, respectively.
[3] | Less accumulated depreciation of $167.5 million and $285.6 million for Alliant Energy as of December 31, 2018 and 2017, respectively.
[4] | Less accumulated amortization of $82.8 million and $77.6 million for WPL as of December 31, 2018 and 2017, respectively. The Sheboygan Falls Energy Facility is eliminated from WPL upon consolidation and is included in the “Non-utility Generation, net” line within Alliant Energy’s consolidated property, plant and equipment.

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