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Property, Plant and Equipment (Property, Plant and Equipment) (Details) - USD ($) $ in Millions | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2019 | Dec. 31, 2017 | Dec. 31, 2016
Property, Plant and Equipment [Line Items] |  |  |  |
Electric plant anticipated to be retired early | [1],[2] |  | $ 93.0 | $ 108.3
Total electric plant |  |  | 12,296.9 | 11,043.5
Gas plant in service |  |  | 1,244.0 | 1,107.6
Other plant in service |  |  | 571.9 | 549.3
Accumulated depreciation |  |  | (4,283.1) | (4,135.7)
Net plant |  |  | 9,829.7 | 8,564.7
Construction work in progress |  |  | 962.2 | 1,226.8
Other, net |  |  | 6.0 | 18.4
Total utility |  |  | 10,797.9 | 9,809.9
Non-utility Generation, net | [3] |  | 90.9 | 135.0
Corporate Services and other, net | [4] |  | 345.7 | 334.3
Total non-utility and other |  |  | 436.6 | 469.3
Total property, plant and equipment |  |  | 11,234.5 | 10,279.2
Non-utility Generation, accumulated depreciation |  |  | 50.5 | 46.5
Corporate Services and other, accumulated depreciation |  |  | 285.6 | 272.0
Generation [Member] |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |
Electric plant in service |  |  | 6,655.3 | 5,866.9
Distribution [Member] |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |
Electric plant in service |  |  | 5,123.5 | 4,739.2
Other [Member] |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |
Electric plant in service |  |  | 425.1 | 329.1
IPL [Member] |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |
Electric plant anticipated to be retired early | [1] |  | 0.0 | 108.3
Total electric plant |  |  | 6,819.1 | 5,837.9
Gas plant in service |  |  | 654.8 | 556.7
Other plant in service |  |  | 333.4 | 313.0
Accumulated depreciation |  |  | (2,311.0) | (2,258.3)
Net plant |  |  | 5,496.3 | 4,449.3
Construction work in progress |  |  | 424.4 | 968.1
Other, net |  |  | 5.5 | 18.2
Total utility |  |  | 5,926.2 | 5,435.6
Total property, plant and equipment |  |  | 5,926.2 | 5,435.6
IPL [Member] | Generation [Member] |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |
Electric plant in service |  |  | 3,715.9 | 2,916.8
IPL [Member] | Distribution [Member] |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |
Electric plant in service |  |  | 2,820.9 | 2,589.3
IPL [Member] | Other [Member] |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |
Electric plant in service |  |  | 282.3 | 223.5
WPL [Member] |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |
Electric plant anticipated to be retired early | [2] |  | 93.0 | 0.0
Total electric plant |  |  | 5,477.8 | 5,205.6
Gas plant in service |  |  | 589.2 | 550.9
Other plant in service |  |  | 238.5 | 236.3
Accumulated depreciation |  |  | (1,972.1) | (1,877.4)
Net plant |  |  | 4,333.4 | 4,115.4
Leased Sheboygan Falls Energy Facility, net | [5] |  | 46.2 | 52.4
Construction work in progress |  |  | 537.8 | 258.7
Other, net |  |  | 0.5 | 0.2
Total utility |  |  | 4,917.9 | 4,426.7
Total property, plant and equipment |  |  | 4,917.9 | 4,426.7
Leased Sheboygan Falls Energy Facility, accumulated depreciation |  |  | 77.6 | 71.4
WPL [Member] | Generation [Member] |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |
Electric plant in service |  |  | 2,939.4 | 2,950.1
WPL [Member] | Distribution [Member] |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |
Electric plant in service |  |  | 2,302.6 | 2,149.9
WPL [Member] | Other [Member] |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |
Electric plant in service |  |  | $ 142.8 | $ 105.6
PSCW [Member] | Scenario, Forecast [Member] | WPL [Member] | Edgewater Unit 4 [Member] |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |
Recovery period, authorized |  | 10 years |  |
[1] | In 2017, IPL retired Sutherland Unit 3 and reclassified the remaining net book value of this EGU from property, plant and equipment to a regulatory asset on Alliant Energy’s and IPL’s balance sheets. Refer to Note 2 for further discussion, including recovery of the remaining net book value of Sutherland Unit 3.
[2] | In 2017, WPL received approval from MISO to retire Edgewater Unit 4 and currently anticipates retiring this EGU by September 30, 2018. In 2016, the PSCW authorized WPL to recover the remaining net book value of Edgewater Unit 4 over a 10-year period beginning the later of the retirement date of the EGU or January 1, 2019.
[3] | Less accumulated depreciation of $50.5 million and $46.5 million for Alliant Energy as of December 31, 2017 and 2016, respectively. Refer to “Franklin County Wind Farm” below for discussion of the April 2017 transfer of the Franklin County wind farm from AEF to IPL pursuant to a February 2017 FERC order.
[4] | Less accumulated depreciation of $285.6 million and $272.0 million for Alliant Energy as of December 31, 2017 and 2016, respectively.
[5] | Less accumulated amortization of $77.6 million and $71.4 million for WPL as of December 31, 2017 and 2016, 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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