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Debt (Tables) | 9 Months Ended
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Sep. 30, 2017
Debt Disclosure [Line Items] |
Other Short-Term Borrowings | Information regarding commercial paper classified as short-term debt was as follows (dollars in millions):
September 30, 2017 | Alliant Energy |  | IPL |  | WPL
Commercial paper outstanding | $390.3 |  | $4.0 |  | $224.6
Commercial paper weighted average interest rates | 1.2% |  | 1.4% |  | 1.1%
Available credit facility capacity (a) | $569.7 |  | $256.0 |  | $175.4
| Alliant Energy |  | IPL |  | WPL
Three Months Ended September 30 | 2017 |  | 2016 |  | 2017 |  | 2016 |  | 2017 |  | 2016
Maximum amount outstanding (based on daily outstanding balances) | $424.4 |  | $248.0 |  | $20.0 |  | $3.1 |  | $271.2 |  | $55.4
Average amount outstanding (based on daily outstanding balances) | $386.2 |  | $220.1 |  | $0.4 |  | $0.1 |  | $217.0 |  | $36.4
Weighted average interest rates | 1.3% |  | 0.6% |  | 1.4% |  | 0.6% |  | 1.1% |  | 0.4%
Nine Months Ended September 30 |  |  |  |  |  |  |  |  |  |  |
Maximum amount outstanding (based on daily outstanding balances) | $424.4 |  | $248.0 |  | $20.0 |  | $3.1 |  | $271.2 |  | $62.9
Average amount outstanding (based on daily outstanding balances) | $323.9 |  | $210.7 |  | $0.5 |  | $— |  | $144.2 |  | $33.2
Weighted average interest rates | 1.1% |  | 0.6% |  | 1.2% |  | 0.6% |  | 1.0% |  | 0.4%
(a) | Alliant Energy’s and IPL’s available credit facility capacities reflect outstanding commercial paper classified as both short- and long-term debt at September 30, 2017.
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):
September 30, 2017 | Alliant Energy |  | IPL |  | WPL
Commercial paper outstanding | $390.3 |  | $4.0 |  | $224.6
Commercial paper weighted average interest rates | 1.2% |  | 1.4% |  | 1.1%
Available credit facility capacity (a) | $569.7 |  | $256.0 |  | $175.4
| Alliant Energy |  | IPL |  | WPL
Three Months Ended September 30 | 2017 |  | 2016 |  | 2017 |  | 2016 |  | 2017 |  | 2016
Maximum amount outstanding (based on daily outstanding balances) | $424.4 |  | $248.0 |  | $20.0 |  | $3.1 |  | $271.2 |  | $55.4
Average amount outstanding (based on daily outstanding balances) | $386.2 |  | $220.1 |  | $0.4 |  | $0.1 |  | $217.0 |  | $36.4
Weighted average interest rates | 1.3% |  | 0.6% |  | 1.4% |  | 0.6% |  | 1.1% |  | 0.4%
Nine Months Ended September 30 |  |  |  |  |  |  |  |  |  |  |
Maximum amount outstanding (based on daily outstanding balances) | $424.4 |  | $248.0 |  | $20.0 |  | $3.1 |  | $271.2 |  | $62.9
Average amount outstanding (based on daily outstanding balances) | $323.9 |  | $210.7 |  | $0.5 |  | $— |  | $144.2 |  | $33.2
Weighted average interest rates | 1.1% |  | 0.6% |  | 1.2% |  | 0.6% |  | 1.0% |  | 0.4%
(a) | Alliant Energy’s and IPL’s available credit facility capacities reflect outstanding commercial paper classified as both short- and long-term debt at September 30, 2017.
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):
September 30, 2017 | Alliant Energy |  | IPL |  | WPL
Commercial paper outstanding | $390.3 |  | $4.0 |  | $224.6
Commercial paper weighted average interest rates | 1.2% |  | 1.4% |  | 1.1%
Available credit facility capacity (a) | $569.7 |  | $256.0 |  | $175.4
| Alliant Energy |  | IPL |  | WPL
Three Months Ended September 30 | 2017 |  | 2016 |  | 2017 |  | 2016 |  | 2017 |  | 2016
Maximum amount outstanding (based on daily outstanding balances) | $424.4 |  | $248.0 |  | $20.0 |  | $3.1 |  | $271.2 |  | $55.4
Average amount outstanding (based on daily outstanding balances) | $386.2 |  | $220.1 |  | $0.4 |  | $0.1 |  | $217.0 |  | $36.4
Weighted average interest rates | 1.3% |  | 0.6% |  | 1.4% |  | 0.6% |  | 1.1% |  | 0.4%
Nine Months Ended September 30 |  |  |  |  |  |  |  |  |  |  |
Maximum amount outstanding (based on daily outstanding balances) | $424.4 |  | $248.0 |  | $20.0 |  | $3.1 |  | $271.2 |  | $62.9
Average amount outstanding (based on daily outstanding balances) | $323.9 |  | $210.7 |  | $0.5 |  | $— |  | $144.2 |  | $33.2
Weighted average interest rates | 1.1% |  | 0.6% |  | 1.2% |  | 0.6% |  | 1.0% |  | 0.4%
(a) | Alliant Energy’s and IPL’s available credit facility capacities reflect outstanding commercial paper classified as both short- and long-term debt at September 30, 2017.

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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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