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Debt (Tables) | 3 Months Ended
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Mar. 31, 2021
Short-term Debt [Line Items] |
Other Short-Term Borrowings | Information regarding Alliant Energy’s, IPL’s and WPL’s commercial paper, and Alliant Energy’s and WPL’s borrowings under the single credit facility, which currently expires in August 2023, classified as short-term debt was as follows (dollars in millions):
March 31, 2021 | Alliant Energy |  | IPL |  | WPL
Amount outstanding | $336 |  | $— |  | $148
Weighted average interest rates | 0.2% |  | N/A |  | 0.1%
Available credit facility capacity | $664 |  | $250 |  | $152
| Alliant Energy |  | IPL |  | WPL
Three Months Ended March 31 | 2021 |  | 2020 |  | 2021 |  | 2020 |  | 2021 |  | 2020
Maximum amount outstanding (based on daily outstanding balances) | $578 |  | $463 |  | $— |  | $1 |  | $275 |  | $212
Average amount outstanding (based on daily outstanding balances) | $424 |  | $382 |  | $— |  | $— |  | $189 |  | $167
Weighted average interest rates | 0.2% |  | 1.8% |  | —% |  | 1.8% |  | 0.2% |  | 1.8%
IPL [Member] |
Short-term Debt [Line Items] |
Other Short-Term Borrowings | Information regarding Alliant Energy’s, IPL’s and WPL’s commercial paper, and Alliant Energy’s and WPL’s borrowings under the single credit facility, which currently expires in August 2023, classified as short-term debt was as follows (dollars in millions):
March 31, 2021 | Alliant Energy |  | IPL |  | WPL
Amount outstanding | $336 |  | $— |  | $148
Weighted average interest rates | 0.2% |  | N/A |  | 0.1%
Available credit facility capacity | $664 |  | $250 |  | $152
| Alliant Energy |  | IPL |  | WPL
Three Months Ended March 31 | 2021 |  | 2020 |  | 2021 |  | 2020 |  | 2021 |  | 2020
Maximum amount outstanding (based on daily outstanding balances) | $578 |  | $463 |  | $— |  | $1 |  | $275 |  | $212
Average amount outstanding (based on daily outstanding balances) | $424 |  | $382 |  | $— |  | $— |  | $189 |  | $167
Weighted average interest rates | 0.2% |  | 1.8% |  | —% |  | 1.8% |  | 0.2% |  | 1.8%
WPL [Member] |
Short-term Debt [Line Items] |
Other Short-Term Borrowings | Information regarding Alliant Energy’s, IPL’s and WPL’s commercial paper, and Alliant Energy’s and WPL’s borrowings under the single credit facility, which currently expires in August 2023, classified as short-term debt was as follows (dollars in millions):
March 31, 2021 | Alliant Energy |  | IPL |  | WPL
Amount outstanding | $336 |  | $— |  | $148
Weighted average interest rates | 0.2% |  | N/A |  | 0.1%
Available credit facility capacity | $664 |  | $250 |  | $152
| Alliant Energy |  | IPL |  | WPL
Three Months Ended March 31 | 2021 |  | 2020 |  | 2021 |  | 2020 |  | 2021 |  | 2020
Maximum amount outstanding (based on daily outstanding balances) | $578 |  | $463 |  | $— |  | $1 |  | $275 |  | $212
Average amount outstanding (based on daily outstanding balances) | $424 |  | $382 |  | $— |  | $— |  | $189 |  | $167
Weighted average interest rates | 0.2% |  | 1.8% |  | —% |  | 1.8% |  | 0.2% |  | 1.8%

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- Definition Tabular disclosure of short-term debt arrangements (having initial terms of repayment within one year or the normal operating cycle, if longer) including: (1) description of the short-term debt arrangement; (2) identification of the lender or type of lender; (3) repayment terms; (4) weighted average interest rate; (5) carrying amount of funds borrowed under the specified short-term debt arrangement as of the balance sheet date; (6) description of the refinancing of a short-term obligation when that obligation is excluded from current liabilities in the balance sheet; and (7) amount of a short-term obligation that has been excluded from current liabilities in the balance sheet because of a refinancing of the obligation. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + 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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