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Leases (Tables) | 12 Months Ended
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Dec. 31, 2020
Leases [Line Items] |
Schedule of Lease Details | At December 31, operating lease details are as follows (dollars in millions):
| 2020 |  | 2019
| Alliant Energy |  | IPL |  | WPL |  | Alliant Energy |  | IPL |  | WPL
Property, plant and equipment, net | $15 |  | $9 |  | $6 |  | $16 |  | $10 |  | $6
Other current liabilities | $2 |  | $1 |  | $1 |  | $2 |  | $1 |  | $1
Other liabilities | 13 |  | 8 |  | 5 |  | 14 |  | 9 |  | 5
Total operating lease liabilities | $15 |  | $9 |  | $6 |  | $16 |  | $10 |  | $6
Weighted average remaining lease term | 10 years |  | 11 years |  | 9 years |  | 11 years |  | 12 years |  | 10 years
Weighted average discount rate | 4% |  | 4% |  | 4% |  | 4% |  | 4% |  | 4%
Schedule of Operating Lease Liability Maturities | As of December 31, 2020, expected maturities of lease liabilities were as follows (in millions):
| 2021 |  | 2022 |  | 2023 |  | 2024 |  | 2025 |  | Thereafter |  | Total |  | Less: amount representing interest |  | Present value of minimum lease payments
Operating Leases: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Alliant Energy | $2 |  |  | $2 |  |  | $2 |  |  | $2 |  |  | $2 |  |  | $8 |  | $18 |  | $3 |  | $15
IPL | 1 |  |  | 1 |  |  | 1 |  |  | 1 |  |  | 1 |  |  | 6 |  | 11 |  | 2 |  | 9
WPL | 1 |  |  | 1 |  |  | 1 |  |  | 1 |  |  | 1 |  |  | 2 |  | 7 |  | 1 |  | 6
WPL’s Finance Lease: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Sheboygan Falls Energy Facility | 15 |  |  | 15 |  |  | 15 |  |  | 15 |  |  | 5 |  |  | — |  | 65 |  | 14 |  | 51
IPL [Member] |
Leases [Line Items] |
Schedule of Lease Details | At December 31, operating lease details are as follows (dollars in millions):
| 2020 |  | 2019
| Alliant Energy |  | IPL |  | WPL |  | Alliant Energy |  | IPL |  | WPL
Property, plant and equipment, net | $15 |  | $9 |  | $6 |  | $16 |  | $10 |  | $6
Other current liabilities | $2 |  | $1 |  | $1 |  | $2 |  | $1 |  | $1
Other liabilities | 13 |  | 8 |  | 5 |  | 14 |  | 9 |  | 5
Total operating lease liabilities | $15 |  | $9 |  | $6 |  | $16 |  | $10 |  | $6
Weighted average remaining lease term | 10 years |  | 11 years |  | 9 years |  | 11 years |  | 12 years |  | 10 years
Weighted average discount rate | 4% |  | 4% |  | 4% |  | 4% |  | 4% |  | 4%
Schedule of Operating Lease Liability Maturities | As of December 31, 2020, expected maturities of lease liabilities were as follows (in millions):
| 2021 |  | 2022 |  | 2023 |  | 2024 |  | 2025 |  | Thereafter |  | Total |  | Less: amount representing interest |  | Present value of minimum lease payments
Operating Leases: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Alliant Energy | $2 |  |  | $2 |  |  | $2 |  |  | $2 |  |  | $2 |  |  | $8 |  | $18 |  | $3 |  | $15
IPL | 1 |  |  | 1 |  |  | 1 |  |  | 1 |  |  | 1 |  |  | 6 |  | 11 |  | 2 |  | 9
WPL | 1 |  |  | 1 |  |  | 1 |  |  | 1 |  |  | 1 |  |  | 2 |  | 7 |  | 1 |  | 6
WPL’s Finance Lease: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Sheboygan Falls Energy Facility | 15 |  |  | 15 |  |  | 15 |  |  | 15 |  |  | 5 |  |  | — |  | 65 |  | 14 |  | 51
WPL [Member] |
Leases [Line Items] |
Schedule of Lease Details | At December 31, operating lease details are as follows (dollars in millions):
| 2020 |  | 2019
| Alliant Energy |  | IPL |  | WPL |  | Alliant Energy |  | IPL |  | WPL
Property, plant and equipment, net | $15 |  | $9 |  | $6 |  | $16 |  | $10 |  | $6
Other current liabilities | $2 |  | $1 |  | $1 |  | $2 |  | $1 |  | $1
Other liabilities | 13 |  | 8 |  | 5 |  | 14 |  | 9 |  | 5
Total operating lease liabilities | $15 |  | $9 |  | $6 |  | $16 |  | $10 |  | $6
Weighted average remaining lease term | 10 years |  | 11 years |  | 9 years |  | 11 years |  | 12 years |  | 10 years
Weighted average discount rate | 4% |  | 4% |  | 4% |  | 4% |  | 4% |  | 4%
WPL’s finance lease details are as follows (dollars in millions):
| December 31, 2020 |  | December 31, 2019
Property, plant and equipment, net | $27 |  | $32
Other current liabilities | $9 |  | $9
Finance lease obligations - Sheboygan Falls Energy Facility | 42 |  | 51
Total finance lease liabilities | $51 |  | $60
Remaining lease term | 4 years |  | 5 years
Discount rate | 11% |  | 11%
| 2020 |  | 2019
Depreciation expense | $6 |  | $6
Interest expense | 6 |  | 7
Total finance lease expense | $12 |  | $13
Schedule of Operating Lease Liability Maturities | As of December 31, 2020, expected maturities of lease liabilities were as follows (in millions):
| 2021 |  | 2022 |  | 2023 |  | 2024 |  | 2025 |  | Thereafter |  | Total |  | Less: amount representing interest |  | Present value of minimum lease payments
Operating Leases: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Alliant Energy | $2 |  |  | $2 |  |  | $2 |  |  | $2 |  |  | $2 |  |  | $8 |  | $18 |  | $3 |  | $15
IPL | 1 |  |  | 1 |  |  | 1 |  |  | 1 |  |  | 1 |  |  | 6 |  | 11 |  | 2 |  | 9
WPL | 1 |  |  | 1 |  |  | 1 |  |  | 1 |  |  | 1 |  |  | 2 |  | 7 |  | 1 |  | 6
WPL’s Finance Lease: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Sheboygan Falls Energy Facility | 15 |  |  | 15 |  |  | 15 |  |  | 15 |  |  | 5 |  |  | — |  | 65 |  | 14 |  | 51
Schedule of Finance Lease Liability Maturities | As of December 31, 2020, expected maturities of lease liabilities were as follows (in millions):
| 2021 |  | 2022 |  | 2023 |  | 2024 |  | 2025 |  | Thereafter |  | Total |  | Less: amount representing interest |  | Present value of minimum lease payments
Operating Leases: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Alliant Energy | $2 |  |  | $2 |  |  | $2 |  |  | $2 |  |  | $2 |  |  | $8 |  | $18 |  | $3 |  | $15
IPL | 1 |  |  | 1 |  |  | 1 |  |  | 1 |  |  | 1 |  |  | 6 |  | 11 |  | 2 |  | 9
WPL | 1 |  |  | 1 |  |  | 1 |  |  | 1 |  |  | 1 |  |  | 2 |  | 7 |  | 1 |  | 6
WPL’s Finance Lease: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Sheboygan Falls Energy Facility | 15 |  |  | 15 |  |  | 15 |  |  | 15 |  |  | 5 |  |  | — |  | 65 |  | 14 |  | 51

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- Definition Tabular disclosure of undiscounted cash flows of finance lease liability. Includes, but is not limited to, reconciliation of undiscounted cash flows to finance lease liability recognized in statement of financial position. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 50 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=121609121&loc=SL77918701-209980 + Details
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- Definition Tabular disclosure of lessee's lease cost. Includes, but is not limited to, interest expense for finance lease, amortization of right-of-use asset for finance lease, operating lease cost, short-term lease cost, variable lease cost and sublease income. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=121609121&loc=SL77918686-209980 + Details
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- Definition Tabular disclosure of undiscounted cash flows of lessee's operating lease liability. Includes, but is not limited to, reconciliation of undiscounted cash flows to operating lease liability recognized in statement of financial position. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 50 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=121609121&loc=SL77918701-209980 + Details
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