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Leases (Tables) | 6 Months Ended
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Jun. 30, 2019
Leases [Line Items] |
Schedule of Lease Details | Operating lease details are as follows (dollars in millions):
| June 30, 2019 |  |  |  |  |  |
| Alliant Energy |  | IPL |  | WPL |  |  |  |  |  |
Property, plant and equipment, net |  | $17 |  |  |  | $10 |  |  |  | $7 |  |  |  |  |  |  |
Other current liabilities |  | $2 |  |  |  | $1 |  |  |  | $1 |  |  |  |  |  |  |
Other liabilities | 15 |  |  | 9 |  |  | 6 |  |  |  |  |  |  |
Total operating lease liabilities |  | $17 |  |  |  | $10 |  |  |  | $7 |  |  |  |  |  |  |
Weighted average remaining lease term | 11 years |  |  | 13 years |  |  | 10 years |  |  |  |  |  |  |
Weighted average discount rate | 4 | % |  | 4 | % |  | 4 | % |  |  |  |  |  |
| Three Months Ended |  | Six Months Ended
| June 30, 2019 |  | June 30, 2019
| Alliant Energy |  | IPL |  | WPL |  | Alliant Energy |  | IPL |  | WPL
Operating lease cost |  | $— |  |  |  | $— |  |  |  | $— |  |  |  | $1 |  |  |  | $— |  |  |  | $— |
Schedule of Operating Lease Liability Maturities | As of June 30, 2019, expected maturities of lease liabilities were as follows (in millions):
| Remainder of 2019 |  | 2020 |  | 2021 |  | 2022 |  | 2023 |  | Thereafter |  | Total |  | Less: amount representing interest |  | Present value of minimum lease payments
Operating Leases: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Alliant Energy |  | $2 |  |  |  | $2 |  |  |  | $2 |  |  |  | $2 |  |  |  | $2 |  |  |  | $13 |  |  |  | $23 |  |  |  | $6 |  |  |  | $17 |
IPL | 1 |  |  | 1 |  |  | 1 |  |  | 1 |  |  | 1 |  |  | 9 |  |  | 14 |  |  | 4 |  |  | 10 |
WPL | 1 |  |  | 1 |  |  | 1 |  |  | 1 |  |  | 1 |  |  | 4 |  |  | 9 |  |  | 2 |  |  | 7 |
WPL’s Finance Lease: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Sheboygan Falls Energy Facility | 7 |  |  | 15 |  |  | 15 |  |  | 15 |  |  | 15 |  |  | 20 |  |  | 87 |  |  | 23 |  |  | 64 |
Schedule of Future Minimum Payments for Operating Leases | As of December 31, 2018, future minimum operating (excluding contingent rentals) and capital lease payments were as follows (in millions):
| 2019 |  | 2020 |  | 2021 |  | 2022 |  | 2023 |  | Thereafter |  | Total |  | Less: amount representing interest |  | Present value of minimum capital lease payments
Operating Leases: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Alliant Energy |  | $5 |  |  |  | $5 |  |  |  | $3 |  |  |  | $3 |  |  |  | $2 |  |  |  | $12 |  |  |  | $30 |  |  |  |  |
IPL | 3 |  |  | 2 |  |  | 2 |  |  | 2 |  |  | 2 |  |  | 12 |  |  | 23 |  |  |  |  |
WPL | 2 |  |  | 3 |  |  | 1 |  |  | — |  |  | — |  |  | — |  |  | 6 |  |  |  |  |
WPL’s Capital Lease: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Sheboygan Falls Energy Facility |  | $15 |  |  |  | $15 |  |  |  | $15 |  |  |  | $15 |  |  |  | $15 |  |  |  | $19 |  |  |  | $94 |  |  |  | $26 |  |  |  | $68 |
IPL [Member] |
Leases [Line Items] |
Schedule of Lease Details | Operating lease details are as follows (dollars in millions):
| June 30, 2019 |  |  |  |  |  |
| Alliant Energy |  | IPL |  | WPL |  |  |  |  |  |
Property, plant and equipment, net |  | $17 |  |  |  | $10 |  |  |  | $7 |  |  |  |  |  |  |
Other current liabilities |  | $2 |  |  |  | $1 |  |  |  | $1 |  |  |  |  |  |  |
Other liabilities | 15 |  |  | 9 |  |  | 6 |  |  |  |  |  |  |
Total operating lease liabilities |  | $17 |  |  |  | $10 |  |  |  | $7 |  |  |  |  |  |  |
Weighted average remaining lease term | 11 years |  |  | 13 years |  |  | 10 years |  |  |  |  |  |  |
Weighted average discount rate | 4 | % |  | 4 | % |  | 4 | % |  |  |  |  |  |
| Three Months Ended |  | Six Months Ended
| June 30, 2019 |  | June 30, 2019
| Alliant Energy |  | IPL |  | WPL |  | Alliant Energy |  | IPL |  | WPL
Operating lease cost |  | $— |  |  |  | $— |  |  |  | $— |  |  |  | $1 |  |  |  | $— |  |  |  | $— |
Schedule of Operating Lease Liability Maturities | As of June 30, 2019, expected maturities of lease liabilities were as follows (in millions):
| Remainder of 2019 |  | 2020 |  | 2021 |  | 2022 |  | 2023 |  | Thereafter |  | Total |  | Less: amount representing interest |  | Present value of minimum lease payments
Operating Leases: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Alliant Energy |  | $2 |  |  |  | $2 |  |  |  | $2 |  |  |  | $2 |  |  |  | $2 |  |  |  | $13 |  |  |  | $23 |  |  |  | $6 |  |  |  | $17 |
IPL | 1 |  |  | 1 |  |  | 1 |  |  | 1 |  |  | 1 |  |  | 9 |  |  | 14 |  |  | 4 |  |  | 10 |
WPL | 1 |  |  | 1 |  |  | 1 |  |  | 1 |  |  | 1 |  |  | 4 |  |  | 9 |  |  | 2 |  |  | 7 |
WPL’s Finance Lease: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Sheboygan Falls Energy Facility | 7 |  |  | 15 |  |  | 15 |  |  | 15 |  |  | 15 |  |  | 20 |  |  | 87 |  |  | 23 |  |  | 64 |
Schedule of Future Minimum Payments for Operating Leases | As of December 31, 2018, future minimum operating (excluding contingent rentals) and capital lease payments were as follows (in millions):
| 2019 |  | 2020 |  | 2021 |  | 2022 |  | 2023 |  | Thereafter |  | Total |  | Less: amount representing interest |  | Present value of minimum capital lease payments
Operating Leases: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Alliant Energy |  | $5 |  |  |  | $5 |  |  |  | $3 |  |  |  | $3 |  |  |  | $2 |  |  |  | $12 |  |  |  | $30 |  |  |  |  |
IPL | 3 |  |  | 2 |  |  | 2 |  |  | 2 |  |  | 2 |  |  | 12 |  |  | 23 |  |  |  |  |
WPL | 2 |  |  | 3 |  |  | 1 |  |  | — |  |  | — |  |  | — |  |  | 6 |  |  |  |  |
WPL’s Capital Lease: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Sheboygan Falls Energy Facility |  | $15 |  |  |  | $15 |  |  |  | $15 |  |  |  | $15 |  |  |  | $15 |  |  |  | $19 |  |  |  | $94 |  |  |  | $26 |  |  |  | $68 |
WPL [Member] |
Leases [Line Items] |
Schedule of Lease Details | WPL’s finance lease details are as follows (dollars in millions):
| June 30, 2019 |  |
Property, plant and equipment, net |  | $35 |  |  |
Other current liabilities |  | $8 |  |  |
Finance lease obligations - Sheboygan Falls Energy Facility | 56 |  |  |
Total finance lease liabilities |  | $64 |  |  |
Remaining lease term | 6 years |  |  |
Discount rate | 11 | % |  |
| Three Months Ended |  | Six Months Ended
| June 30, 2019 |  | June 30, 2019
Depreciation expense |  | $2 |  |  |  | $3 |
Interest expense | 2 |  |  | 4 |
Total finance lease expense |  | $4 |  |  |  | $7 |
Operating lease details are as follows (dollars in millions):
| June 30, 2019 |  |  |  |  |  |
| Alliant Energy |  | IPL |  | WPL |  |  |  |  |  |
Property, plant and equipment, net |  | $17 |  |  |  | $10 |  |  |  | $7 |  |  |  |  |  |  |
Other current liabilities |  | $2 |  |  |  | $1 |  |  |  | $1 |  |  |  |  |  |  |
Other liabilities | 15 |  |  | 9 |  |  | 6 |  |  |  |  |  |  |
Total operating lease liabilities |  | $17 |  |  |  | $10 |  |  |  | $7 |  |  |  |  |  |  |
Weighted average remaining lease term | 11 years |  |  | 13 years |  |  | 10 years |  |  |  |  |  |  |
Weighted average discount rate | 4 | % |  | 4 | % |  | 4 | % |  |  |  |  |  |
| Three Months Ended |  | Six Months Ended
| June 30, 2019 |  | June 30, 2019
| Alliant Energy |  | IPL |  | WPL |  | Alliant Energy |  | IPL |  | WPL
Operating lease cost |  | $— |  |  |  | $— |  |  |  | $— |  |  |  | $1 |  |  |  | $— |  |  |  | $— |
Schedule of Operating Lease Liability Maturities | As of June 30, 2019, expected maturities of lease liabilities were as follows (in millions):
| Remainder of 2019 |  | 2020 |  | 2021 |  | 2022 |  | 2023 |  | Thereafter |  | Total |  | Less: amount representing interest |  | Present value of minimum lease payments
Operating Leases: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Alliant Energy |  | $2 |  |  |  | $2 |  |  |  | $2 |  |  |  | $2 |  |  |  | $2 |  |  |  | $13 |  |  |  | $23 |  |  |  | $6 |  |  |  | $17 |
IPL | 1 |  |  | 1 |  |  | 1 |  |  | 1 |  |  | 1 |  |  | 9 |  |  | 14 |  |  | 4 |  |  | 10 |
WPL | 1 |  |  | 1 |  |  | 1 |  |  | 1 |  |  | 1 |  |  | 4 |  |  | 9 |  |  | 2 |  |  | 7 |
WPL’s Finance Lease: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Sheboygan Falls Energy Facility | 7 |  |  | 15 |  |  | 15 |  |  | 15 |  |  | 15 |  |  | 20 |  |  | 87 |  |  | 23 |  |  | 64 |
Schedule of Finance Lease Liability Maturities | As of June 30, 2019, expected maturities of lease liabilities were as follows (in millions):
| Remainder of 2019 |  | 2020 |  | 2021 |  | 2022 |  | 2023 |  | Thereafter |  | Total |  | Less: amount representing interest |  | Present value of minimum lease payments
Operating Leases: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Alliant Energy |  | $2 |  |  |  | $2 |  |  |  | $2 |  |  |  | $2 |  |  |  | $2 |  |  |  | $13 |  |  |  | $23 |  |  |  | $6 |  |  |  | $17 |
IPL | 1 |  |  | 1 |  |  | 1 |  |  | 1 |  |  | 1 |  |  | 9 |  |  | 14 |  |  | 4 |  |  | 10 |
WPL | 1 |  |  | 1 |  |  | 1 |  |  | 1 |  |  | 1 |  |  | 4 |  |  | 9 |  |  | 2 |  |  | 7 |
WPL’s Finance Lease: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Sheboygan Falls Energy Facility | 7 |  |  | 15 |  |  | 15 |  |  | 15 |  |  | 15 |  |  | 20 |  |  | 87 |  |  | 23 |  |  | 64 |
Schedule of Future Minimum Payments for Operating Leases | As of December 31, 2018, future minimum operating (excluding contingent rentals) and capital lease payments were as follows (in millions):
| 2019 |  | 2020 |  | 2021 |  | 2022 |  | 2023 |  | Thereafter |  | Total |  | Less: amount representing interest |  | Present value of minimum capital lease payments
Operating Leases: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Alliant Energy |  | $5 |  |  |  | $5 |  |  |  | $3 |  |  |  | $3 |  |  |  | $2 |  |  |  | $12 |  |  |  | $30 |  |  |  |  |
IPL | 3 |  |  | 2 |  |  | 2 |  |  | 2 |  |  | 2 |  |  | 12 |  |  | 23 |  |  |  |  |
WPL | 2 |  |  | 3 |  |  | 1 |  |  | — |  |  | — |  |  | — |  |  | 6 |  |  |  |  |
WPL’s Capital Lease: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Sheboygan Falls Energy Facility |  | $15 |  |  |  | $15 |  |  |  | $15 |  |  |  | $15 |  |  |  | $15 |  |  |  | $19 |  |  |  | $94 |  |  |  | $26 |  |  |  | $68 |
Schedule of Future Minimum Payments for Capital Leases | As of December 31, 2018, future minimum operating (excluding contingent rentals) and capital lease payments were as follows (in millions):
| 2019 |  | 2020 |  | 2021 |  | 2022 |  | 2023 |  | Thereafter |  | Total |  | Less: amount representing interest |  | Present value of minimum capital lease payments
Operating Leases: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Alliant Energy |  | $5 |  |  |  | $5 |  |  |  | $3 |  |  |  | $3 |  |  |  | $2 |  |  |  | $12 |  |  |  | $30 |  |  |  |  |
IPL | 3 |  |  | 2 |  |  | 2 |  |  | 2 |  |  | 2 |  |  | 12 |  |  | 23 |  |  |  |  |
WPL | 2 |  |  | 3 |  |  | 1 |  |  | — |  |  | — |  |  | — |  |  | 6 |  |  |  |  |
WPL’s Capital Lease: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Sheboygan Falls Energy Facility |  | $15 |  |  |  | $15 |  |  |  | $15 |  |  |  | $15 |  |  |  | $15 |  |  |  | $19 |  |  |  | $94 |  |  |  | $26 |  |  |  | $68 |

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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=77888426&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=77888426&loc=SL77918686-209980 + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + 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=77888426&loc=SL77918701-209980 + Details
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- Definition Tabular disclosure of future minimum lease payments as of the date of the latest balance sheet presented, in aggregate and for each of the five years succeeding fiscal years, with separate deductions from the total for the amount representing executor costs, including any profit thereon, included in the minimum lease payments and for the amount of the imputed interest necessary to reduce the net minimum lease payments to present value. + References Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 30 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=84164817&loc=d3e45280-112737 + Details
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- Definition Tabular disclosure of future minimum payments required in the aggregate and for each of the five succeeding fiscal years for operating leases having initial or remaining noncancelable lease terms in excess of one year and the total minimum rentals to be received in the future under noncancelable subleases as of the balance sheet date. + References Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 20 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=77902758&loc=d3e41502-112717 + Details
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