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Property, Plant and Equipment (Tables) | 12 Months Ended
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Dec. 31, 2016
Property, Plant and Equipment [Line Items] |
Property, Plant and Equipment | At December 31, details of property, plant and equipment on the balance sheets were as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2016 |  | 2015 |  | 2016 |  | 2015 |  | 2016 |  | 2015
Utility: |  |  |  |  |  |  |  |  |  |  |
Electric plant: |  |  |  |  |  |  |  |  |  |  |
Generation in service |  | $5,866.9 |  |  |  | $5,643.7 |  |  |  | $2,916.8 |  |  |  | $3,011.6 |  |  |  | $2,950.1 |  |  |  | $2,632.1 |
Distribution in service | 4,739.2 |  |  | 4,489.9 |  |  | 2,589.3 |  |  | 2,447.9 |  |  | 2,149.9 |  |  | 2,042.0 |
Other in service | 329.1 |  |  | 311.3 |  |  | 223.5 |  |  | 212.2 |  |  | 105.6 |  |  | 99.1 |
Anticipated to be retired early (a) | 108.3 |  |  | — |  |  | 108.3 |  |  | — |  |  | — |  |  | — |
Total electric plant | 11,043.5 |  |  | 10,444.9 |  |  | 5,837.9 |  |  | 5,671.7 |  |  | 5,205.6 |  |  | 4,773.2 |
Gas plant in service | 1,107.6 |  |  | 1,018.3 |  |  | 556.7 |  |  | 513.6 |  |  | 550.9 |  |  | 504.7 |
Other plant in service | 549.3 |  |  | 530.6 |  |  | 313.0 |  |  | 296.0 |  |  | 236.3 |  |  | 234.6 |
Accumulated depreciation | (4,135.7 | ) |  | (3,939.6 | ) |  | (2,258.3 | ) |  | (2,152.8 | ) |  | (1,877.4 | ) |  | (1,786.8 | )
Net plant | 8,564.7 |  |  | 8,054.2 |  |  | 4,449.3 |  |  | 4,328.5 |  |  | 4,115.4 |  |  | 3,725.7 |
Leased Sheboygan Falls Energy Facility, net (b) | — |  |  | — |  |  | — |  |  | — |  |  | 52.4 |  |  | 58.6 |
Construction work in progress | 1,226.8 |  |  | 897.5 |  |  | 968.1 |  |  | 578.2 |  |  | 258.7 |  |  | 319.3 |
Other, net | 18.4 |  |  | 18.5 |  |  | 18.2 |  |  | 18.4 |  |  | 0.2 |  |  | 0.1 |
Total utility | 9,809.9 |  |  | 8,970.2 |  |  | 5,435.6 |  |  | 4,925.1 |  |  | 4,426.7 |  |  | 4,103.7 |
Non-regulated and other: |  |  |  |  |  |  |  |  |  |  |
Non-regulated Generation, net (c) | 135.0 |  |  | 229.3 |  |  | — |  |  | — |  |  | — |  |  | — |
Corporate Services and other, net (d) | 334.3 |  |  | 319.6 |  |  | — |  |  | — |  |  | — |  |  | — |
Total non-regulated and other | 469.3 |  |  | 548.9 |  |  | — |  |  | — |  |  | — |  |  | — |
Total property, plant and equipment |  | $10,279.2 |  |  |  | $9,519.1 |  |  |  | $5,435.6 |  |  |  | $4,925.1 |  |  |  | $4,426.7 |  |  |  | $4,103.7 |
(a) | In 2016, IPL received approval from MISO to retire Sutherland Unit 3 and currently anticipates retiring this EGU by June 30, 2017. The recovery of the remaining net book value of this EGU is expected to be addressed in IPL’s next retail electric base rate case, which is currently expected to be filed in the second quarter of 2017.
(b) | Less accumulated amortization of $71.4 million and $65.2 million for WPL as of December 31, 2016 and 2015, respectively. The Sheboygan Falls Energy Facility is eliminated from WPL upon consolidation and is included in the “Non-regulated Generation, net” line within Alliant Energy’s consolidated property, plant and equipment.
(c) | Less accumulated depreciation of $46.5 million and $59.0 million for Alliant Energy as of December 31, 2016 and 2015, respectively.
(d) | Less accumulated depreciation of $272.0 million and $252.9 million for Alliant Energy as of December 31, 2016 and 2015, respectively.
Schedule Of Allowance For Funds Used During Construction | The amount of AFUDC generated by equity and debt components was as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2016 |  | 2015 |  | 2014 |  | 2016 |  | 2015 |  | 2014 |  | 2016 |  | 2015 |  | 2014
Equity |  | $42.3 |  |  |  | $24.4 |  |  |  | $23.1 |  |  |  | $35.2 |  |  |  | $18.6 |  |  |  | $17.1 |  |  |  | $7.1 |  |  |  | $5.8 |  |  |  | $6.0 |
Debt | 20.2 |  |  | 12.5 |  |  | 11.7 |  |  | 16.8 |  |  | 9.6 |  |  | 8.8 |  |  | 3.4 |  |  | 2.9 |  |  | 2.9 |
|  | $62.5 |  |  |  | $36.9 |  |  |  | $34.8 |  |  |  | $52.0 |  |  |  | $28.2 |  |  |  | $25.9 |  |  |  | $10.5 |  |  |  | $8.7 |  |  |  | $8.9 |
Schedule Of Allowance for Funds Used During Construction By Project | AFUDC related to various construction projects was recognized in the income statements as follows (in millions):
| 2016 |  | 2015 |  | 2014
IPL: |  |  |  |  |
Marshalltown |  | $43.8 |  |  |  | $20.7 |  |  |  | $3.7 |
Environmental controls - Ottumwa Unit 1 | — |  |  | — |  |  | 10.6 |
Other | 8.2 |  |  | 7.5 |  |  | 11.6 |
| 52.0 |  |  | 28.2 |  |  | 25.9 |
WPL: |  |  |  |  |
Environmental controls - Edgewater Unit 5 | 4.3 |  |  | 5.1 |  |  | 2.7 |
Other | 6.2 |  |  | 3.6 |  |  | 6.2 |
| 10.5 |  |  | 8.7 |  |  | 8.9 |
Alliant Energy |  | $62.5 |  |  |  | $36.9 |  |  |  | $34.8 |
IPL [Member] |
Property, Plant and Equipment [Line Items] |
Property, Plant and Equipment | At December 31, details of property, plant and equipment on the balance sheets were as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2016 |  | 2015 |  | 2016 |  | 2015 |  | 2016 |  | 2015
Utility: |  |  |  |  |  |  |  |  |  |  |
Electric plant: |  |  |  |  |  |  |  |  |  |  |
Generation in service |  | $5,866.9 |  |  |  | $5,643.7 |  |  |  | $2,916.8 |  |  |  | $3,011.6 |  |  |  | $2,950.1 |  |  |  | $2,632.1 |
Distribution in service | 4,739.2 |  |  | 4,489.9 |  |  | 2,589.3 |  |  | 2,447.9 |  |  | 2,149.9 |  |  | 2,042.0 |
Other in service | 329.1 |  |  | 311.3 |  |  | 223.5 |  |  | 212.2 |  |  | 105.6 |  |  | 99.1 |
Anticipated to be retired early (a) | 108.3 |  |  | — |  |  | 108.3 |  |  | — |  |  | — |  |  | — |
Total electric plant | 11,043.5 |  |  | 10,444.9 |  |  | 5,837.9 |  |  | 5,671.7 |  |  | 5,205.6 |  |  | 4,773.2 |
Gas plant in service | 1,107.6 |  |  | 1,018.3 |  |  | 556.7 |  |  | 513.6 |  |  | 550.9 |  |  | 504.7 |
Other plant in service | 549.3 |  |  | 530.6 |  |  | 313.0 |  |  | 296.0 |  |  | 236.3 |  |  | 234.6 |
Accumulated depreciation | (4,135.7 | ) |  | (3,939.6 | ) |  | (2,258.3 | ) |  | (2,152.8 | ) |  | (1,877.4 | ) |  | (1,786.8 | )
Net plant | 8,564.7 |  |  | 8,054.2 |  |  | 4,449.3 |  |  | 4,328.5 |  |  | 4,115.4 |  |  | 3,725.7 |
Leased Sheboygan Falls Energy Facility, net (b) | — |  |  | — |  |  | — |  |  | — |  |  | 52.4 |  |  | 58.6 |
Construction work in progress | 1,226.8 |  |  | 897.5 |  |  | 968.1 |  |  | 578.2 |  |  | 258.7 |  |  | 319.3 |
Other, net | 18.4 |  |  | 18.5 |  |  | 18.2 |  |  | 18.4 |  |  | 0.2 |  |  | 0.1 |
Total utility | 9,809.9 |  |  | 8,970.2 |  |  | 5,435.6 |  |  | 4,925.1 |  |  | 4,426.7 |  |  | 4,103.7 |
Non-regulated and other: |  |  |  |  |  |  |  |  |  |  |
Non-regulated Generation, net (c) | 135.0 |  |  | 229.3 |  |  | — |  |  | — |  |  | — |  |  | — |
Corporate Services and other, net (d) | 334.3 |  |  | 319.6 |  |  | — |  |  | — |  |  | — |  |  | — |
Total non-regulated and other | 469.3 |  |  | 548.9 |  |  | — |  |  | — |  |  | — |  |  | — |
Total property, plant and equipment |  | $10,279.2 |  |  |  | $9,519.1 |  |  |  | $5,435.6 |  |  |  | $4,925.1 |  |  |  | $4,426.7 |  |  |  | $4,103.7 |
(a) | In 2016, IPL received approval from MISO to retire Sutherland Unit 3 and currently anticipates retiring this EGU by June 30, 2017. The recovery of the remaining net book value of this EGU is expected to be addressed in IPL’s next retail electric base rate case, which is currently expected to be filed in the second quarter of 2017.
(b) | Less accumulated amortization of $71.4 million and $65.2 million for WPL as of December 31, 2016 and 2015, respectively. The Sheboygan Falls Energy Facility is eliminated from WPL upon consolidation and is included in the “Non-regulated Generation, net” line within Alliant Energy’s consolidated property, plant and equipment.
(c) | Less accumulated depreciation of $46.5 million and $59.0 million for Alliant Energy as of December 31, 2016 and 2015, respectively.
(d) | Less accumulated depreciation of $272.0 million and $252.9 million for Alliant Energy as of December 31, 2016 and 2015, respectively.
Schedule Of Allowance For Funds Used During Construction | The amount of AFUDC generated by equity and debt components was as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2016 |  | 2015 |  | 2014 |  | 2016 |  | 2015 |  | 2014 |  | 2016 |  | 2015 |  | 2014
Equity |  | $42.3 |  |  |  | $24.4 |  |  |  | $23.1 |  |  |  | $35.2 |  |  |  | $18.6 |  |  |  | $17.1 |  |  |  | $7.1 |  |  |  | $5.8 |  |  |  | $6.0 |
Debt | 20.2 |  |  | 12.5 |  |  | 11.7 |  |  | 16.8 |  |  | 9.6 |  |  | 8.8 |  |  | 3.4 |  |  | 2.9 |  |  | 2.9 |
|  | $62.5 |  |  |  | $36.9 |  |  |  | $34.8 |  |  |  | $52.0 |  |  |  | $28.2 |  |  |  | $25.9 |  |  |  | $10.5 |  |  |  | $8.7 |  |  |  | $8.9 |
Schedule Of Allowance for Funds Used During Construction By Project | AFUDC related to various construction projects was recognized in the income statements as follows (in millions):
| 2016 |  | 2015 |  | 2014
IPL: |  |  |  |  |
Marshalltown |  | $43.8 |  |  |  | $20.7 |  |  |  | $3.7 |
Environmental controls - Ottumwa Unit 1 | — |  |  | — |  |  | 10.6 |
Other | 8.2 |  |  | 7.5 |  |  | 11.6 |
| 52.0 |  |  | 28.2 |  |  | 25.9 |
WPL: |  |  |  |  |
Environmental controls - Edgewater Unit 5 | 4.3 |  |  | 5.1 |  |  | 2.7 |
Other | 6.2 |  |  | 3.6 |  |  | 6.2 |
| 10.5 |  |  | 8.7 |  |  | 8.9 |
Alliant Energy |  | $62.5 |  |  |  | $36.9 |  |  |  | $34.8 |
WPL [Member] |
Property, Plant and Equipment [Line Items] |
Property, Plant and Equipment | At December 31, details of property, plant and equipment on the balance sheets were as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2016 |  | 2015 |  | 2016 |  | 2015 |  | 2016 |  | 2015
Utility: |  |  |  |  |  |  |  |  |  |  |
Electric plant: |  |  |  |  |  |  |  |  |  |  |
Generation in service |  | $5,866.9 |  |  |  | $5,643.7 |  |  |  | $2,916.8 |  |  |  | $3,011.6 |  |  |  | $2,950.1 |  |  |  | $2,632.1 |
Distribution in service | 4,739.2 |  |  | 4,489.9 |  |  | 2,589.3 |  |  | 2,447.9 |  |  | 2,149.9 |  |  | 2,042.0 |
Other in service | 329.1 |  |  | 311.3 |  |  | 223.5 |  |  | 212.2 |  |  | 105.6 |  |  | 99.1 |
Anticipated to be retired early (a) | 108.3 |  |  | — |  |  | 108.3 |  |  | — |  |  | — |  |  | — |
Total electric plant | 11,043.5 |  |  | 10,444.9 |  |  | 5,837.9 |  |  | 5,671.7 |  |  | 5,205.6 |  |  | 4,773.2 |
Gas plant in service | 1,107.6 |  |  | 1,018.3 |  |  | 556.7 |  |  | 513.6 |  |  | 550.9 |  |  | 504.7 |
Other plant in service | 549.3 |  |  | 530.6 |  |  | 313.0 |  |  | 296.0 |  |  | 236.3 |  |  | 234.6 |
Accumulated depreciation | (4,135.7 | ) |  | (3,939.6 | ) |  | (2,258.3 | ) |  | (2,152.8 | ) |  | (1,877.4 | ) |  | (1,786.8 | )
Net plant | 8,564.7 |  |  | 8,054.2 |  |  | 4,449.3 |  |  | 4,328.5 |  |  | 4,115.4 |  |  | 3,725.7 |
Leased Sheboygan Falls Energy Facility, net (b) | — |  |  | — |  |  | — |  |  | — |  |  | 52.4 |  |  | 58.6 |
Construction work in progress | 1,226.8 |  |  | 897.5 |  |  | 968.1 |  |  | 578.2 |  |  | 258.7 |  |  | 319.3 |
Other, net | 18.4 |  |  | 18.5 |  |  | 18.2 |  |  | 18.4 |  |  | 0.2 |  |  | 0.1 |
Total utility | 9,809.9 |  |  | 8,970.2 |  |  | 5,435.6 |  |  | 4,925.1 |  |  | 4,426.7 |  |  | 4,103.7 |
Non-regulated and other: |  |  |  |  |  |  |  |  |  |  |
Non-regulated Generation, net (c) | 135.0 |  |  | 229.3 |  |  | — |  |  | — |  |  | — |  |  | — |
Corporate Services and other, net (d) | 334.3 |  |  | 319.6 |  |  | — |  |  | — |  |  | — |  |  | — |
Total non-regulated and other | 469.3 |  |  | 548.9 |  |  | — |  |  | — |  |  | — |  |  | — |
Total property, plant and equipment |  | $10,279.2 |  |  |  | $9,519.1 |  |  |  | $5,435.6 |  |  |  | $4,925.1 |  |  |  | $4,426.7 |  |  |  | $4,103.7 |
(a) | In 2016, IPL received approval from MISO to retire Sutherland Unit 3 and currently anticipates retiring this EGU by June 30, 2017. The recovery of the remaining net book value of this EGU is expected to be addressed in IPL’s next retail electric base rate case, which is currently expected to be filed in the second quarter of 2017.
(b) | Less accumulated amortization of $71.4 million and $65.2 million for WPL as of December 31, 2016 and 2015, respectively. The Sheboygan Falls Energy Facility is eliminated from WPL upon consolidation and is included in the “Non-regulated Generation, net” line within Alliant Energy’s consolidated property, plant and equipment.
(c) | Less accumulated depreciation of $46.5 million and $59.0 million for Alliant Energy as of December 31, 2016 and 2015, respectively.
(d) | Less accumulated depreciation of $272.0 million and $252.9 million for Alliant Energy as of December 31, 2016 and 2015, respectively.
Schedule Of Allowance For Funds Used During Construction | The amount of AFUDC generated by equity and debt components was as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2016 |  | 2015 |  | 2014 |  | 2016 |  | 2015 |  | 2014 |  | 2016 |  | 2015 |  | 2014
Equity |  | $42.3 |  |  |  | $24.4 |  |  |  | $23.1 |  |  |  | $35.2 |  |  |  | $18.6 |  |  |  | $17.1 |  |  |  | $7.1 |  |  |  | $5.8 |  |  |  | $6.0 |
Debt | 20.2 |  |  | 12.5 |  |  | 11.7 |  |  | 16.8 |  |  | 9.6 |  |  | 8.8 |  |  | 3.4 |  |  | 2.9 |  |  | 2.9 |
|  | $62.5 |  |  |  | $36.9 |  |  |  | $34.8 |  |  |  | $52.0 |  |  |  | $28.2 |  |  |  | $25.9 |  |  |  | $10.5 |  |  |  | $8.7 |  |  |  | $8.9 |
Schedule Of Allowance for Funds Used During Construction By Project | AFUDC related to various construction projects was recognized in the income statements as follows (in millions):
| 2016 |  | 2015 |  | 2014
IPL: |  |  |  |  |
Marshalltown |  | $43.8 |  |  |  | $20.7 |  |  |  | $3.7 |
Environmental controls - Ottumwa Unit 1 | — |  |  | — |  |  | 10.6 |
Other | 8.2 |  |  | 7.5 |  |  | 11.6 |
| 52.0 |  |  | 28.2 |  |  | 25.9 |
WPL: |  |  |  |  |
Environmental controls - Edgewater Unit 5 | 4.3 |  |  | 5.1 |  |  | 2.7 |
Other | 6.2 |  |  | 3.6 |  |  | 6.2 |
| 10.5 |  |  | 8.7 |  |  | 8.9 |
Alliant Energy |  | $62.5 |  |  |  | $36.9 |  |  |  | $34.8 |

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