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Debt (Tables) | 3 Months Ended
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Mar. 31, 2018
Debt Disclosure [Line Items] |
Other Short-Term Borrowings | Information regarding commercial paper classified as short-term debt was as follows (dollars in millions):
March 31, 2018 | Alliant Energy |  | IPL |  | WPL
Commercial paper outstanding | $336.4 |  | $— |  | $30.6
Commercial paper weighted average interest rates | 2.3% |  | N/A |  | 1.8%
Available credit facility capacity (a) | $617.7 |  | $204.1 |  | $319.4
| Alliant Energy |  | IPL |  | WPL
Three Months Ended March 31 | 2018 |  | 2017 |  | 2018 |  | 2017 |  | 2018 |  | 2017
Maximum amount outstanding (based on daily outstanding balances) | $336.4 |  | $325.5 |  | $3.0 |  | $9.2 |  | $36.7 |  | $113.6
Average amount outstanding (based on daily outstanding balances) | $310.1 |  | $276.5 |  | $— |  | $0.1 |  | $11.5 |  | $79.1
Weighted average interest rates | 1.9% |  | 0.9% |  | 1.8% |  | 1.1% |  | 1.6% |  | 0.7%
(a) | Alliant Energy’s and IPL’s available credit facility capacities reflect outstanding commercial paper classified as both short- and long-term debt at March 31, 2018.
IPL [Member] |
Debt Disclosure [Line Items] |
Other Short-Term Borrowings | Information regarding commercial paper classified as short-term debt was as follows (dollars in millions):
March 31, 2018 | Alliant Energy |  | IPL |  | WPL
Commercial paper outstanding | $336.4 |  | $— |  | $30.6
Commercial paper weighted average interest rates | 2.3% |  | N/A |  | 1.8%
Available credit facility capacity (a) | $617.7 |  | $204.1 |  | $319.4
| Alliant Energy |  | IPL |  | WPL
Three Months Ended March 31 | 2018 |  | 2017 |  | 2018 |  | 2017 |  | 2018 |  | 2017
Maximum amount outstanding (based on daily outstanding balances) | $336.4 |  | $325.5 |  | $3.0 |  | $9.2 |  | $36.7 |  | $113.6
Average amount outstanding (based on daily outstanding balances) | $310.1 |  | $276.5 |  | $— |  | $0.1 |  | $11.5 |  | $79.1
Weighted average interest rates | 1.9% |  | 0.9% |  | 1.8% |  | 1.1% |  | 1.6% |  | 0.7%
(a) | Alliant Energy’s and IPL’s available credit facility capacities reflect outstanding commercial paper classified as both short- and long-term debt at March 31, 2018.
WPL [Member] |
Debt Disclosure [Line Items] |
Other Short-Term Borrowings | Information regarding commercial paper classified as short-term debt was as follows (dollars in millions):
March 31, 2018 | Alliant Energy |  | IPL |  | WPL
Commercial paper outstanding | $336.4 |  | $— |  | $30.6
Commercial paper weighted average interest rates | 2.3% |  | N/A |  | 1.8%
Available credit facility capacity (a) | $617.7 |  | $204.1 |  | $319.4
| Alliant Energy |  | IPL |  | WPL
Three Months Ended March 31 | 2018 |  | 2017 |  | 2018 |  | 2017 |  | 2018 |  | 2017
Maximum amount outstanding (based on daily outstanding balances) | $336.4 |  | $325.5 |  | $3.0 |  | $9.2 |  | $36.7 |  | $113.6
Average amount outstanding (based on daily outstanding balances) | $310.1 |  | $276.5 |  | $— |  | $0.1 |  | $11.5 |  | $79.1
Weighted average interest rates | 1.9% |  | 0.9% |  | 1.8% |  | 1.1% |  | 1.6% |  | 0.7%
(a) | Alliant Energy’s and IPL’s available credit facility capacities reflect outstanding commercial paper classified as both short- and long-term debt at March 31, 2018.

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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://www.xbrl.org/2003/role/presentationRef -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=6877327&loc=d3e13212-122682 + Details
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