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Debt (Tables) | 9 Months Ended
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Sep. 30, 2015
Debt Disclosure [Line Items] |
Other Short-Term Borrowings | Information regarding commercial paper classified as short-term debt and back-stopped by the credit facilities was as follows (dollars in millions):
| Alliant Energy |  | Parent |  |  |  |
September 30, 2015 | (Consolidated) |  | Company |  | IPL |  | WPL
Commercial paper: |  |  |  |  |  |  |
Amount outstanding | $109.1 |  | $109.1 |  | $— |  | $—
Weighted average remaining maturity | 3 days |  | 3 days |  | N/A |  | N/A
Weighted average interest rates | 0.4% |  | 0.4% |  | N/A |  | N/A
Available credit facility capacity | $890.9 |  | $190.9 |  | $300.0 |  | $400.0
| Alliant Energy |  | IPL |  | WPL
Three Months Ended September 30 | 2015 |  | 2014 |  | 2015 |  | 2014 |  | 2015 |  | 2014
Maximum amount outstanding (based on daily outstanding balances) |  | $181.2 |  |  |  | $353.8 |  |  |  | $18.4 |  |  |  | $38.0 |  |  | $— |  |  | $185.0 |
Average amount outstanding (based on daily outstanding balances) |  | $122.4 |  |  |  | $307.1 |  |  |  | $0.5 |  |  |  | $0.4 |  |  | $— |  |  | $157.9 |
Weighted average interest rates | 0.4 | % |  | 0.2 | % |  | 0.4 | % |  | 0.3 | % |  | N/A |  | 0.1 | %
Nine Months Ended September 30 |  |  |  |  |  |  |  |  |  |  |
Maximum amount outstanding (based on daily outstanding balances) |  | $181.2 |  |  |  | $353.8 |  |  |  | $18.4 |  |  |  | $38.0 |  |  | $— |  |  | $204.7 |
Average amount outstanding (based on daily outstanding balances) |  | $114.5 |  |  |  | $281.9 |  |  |  | $0.2 |  |  |  | $0.3 |  |  | $— |  |  | $157.5 |
Weighted average interest rates | 0.4 | % |  | 0.2 | % |  | 0.4 | % |  | 0.2 | % |  | N/A |  | 0.1 | %
IPL [Member] |
Debt Disclosure [Line Items] |
Other Short-Term Borrowings | Information regarding commercial paper classified as short-term debt and back-stopped by the credit facilities was as follows (dollars in millions):
| Alliant Energy |  | Parent |  |  |  |
September 30, 2015 | (Consolidated) |  | Company |  | IPL |  | WPL
Commercial paper: |  |  |  |  |  |  |
Amount outstanding | $109.1 |  | $109.1 |  | $— |  | $—
Weighted average remaining maturity | 3 days |  | 3 days |  | N/A |  | N/A
Weighted average interest rates | 0.4% |  | 0.4% |  | N/A |  | N/A
Available credit facility capacity | $890.9 |  | $190.9 |  | $300.0 |  | $400.0
| Alliant Energy |  | IPL |  | WPL
Three Months Ended September 30 | 2015 |  | 2014 |  | 2015 |  | 2014 |  | 2015 |  | 2014
Maximum amount outstanding (based on daily outstanding balances) |  | $181.2 |  |  |  | $353.8 |  |  |  | $18.4 |  |  |  | $38.0 |  |  | $— |  |  | $185.0 |
Average amount outstanding (based on daily outstanding balances) |  | $122.4 |  |  |  | $307.1 |  |  |  | $0.5 |  |  |  | $0.4 |  |  | $— |  |  | $157.9 |
Weighted average interest rates | 0.4 | % |  | 0.2 | % |  | 0.4 | % |  | 0.3 | % |  | N/A |  | 0.1 | %
Nine Months Ended September 30 |  |  |  |  |  |  |  |  |  |  |
Maximum amount outstanding (based on daily outstanding balances) |  | $181.2 |  |  |  | $353.8 |  |  |  | $18.4 |  |  |  | $38.0 |  |  | $— |  |  | $204.7 |
Average amount outstanding (based on daily outstanding balances) |  | $114.5 |  |  |  | $281.9 |  |  |  | $0.2 |  |  |  | $0.3 |  |  | $— |  |  | $157.5 |
Weighted average interest rates | 0.4 | % |  | 0.2 | % |  | 0.4 | % |  | 0.2 | % |  | N/A |  | 0.1 | %
WPL [Member] |
Debt Disclosure [Line Items] |
Other Short-Term Borrowings | Information regarding commercial paper classified as short-term debt and back-stopped by the credit facilities was as follows (dollars in millions):
| Alliant Energy |  | Parent |  |  |  |
September 30, 2015 | (Consolidated) |  | Company |  | IPL |  | WPL
Commercial paper: |  |  |  |  |  |  |
Amount outstanding | $109.1 |  | $109.1 |  | $— |  | $—
Weighted average remaining maturity | 3 days |  | 3 days |  | N/A |  | N/A
Weighted average interest rates | 0.4% |  | 0.4% |  | N/A |  | N/A
Available credit facility capacity | $890.9 |  | $190.9 |  | $300.0 |  | $400.0
| Alliant Energy |  | IPL |  | WPL
Three Months Ended September 30 | 2015 |  | 2014 |  | 2015 |  | 2014 |  | 2015 |  | 2014
Maximum amount outstanding (based on daily outstanding balances) |  | $181.2 |  |  |  | $353.8 |  |  |  | $18.4 |  |  |  | $38.0 |  |  | $— |  |  | $185.0 |
Average amount outstanding (based on daily outstanding balances) |  | $122.4 |  |  |  | $307.1 |  |  |  | $0.5 |  |  |  | $0.4 |  |  | $— |  |  | $157.9 |
Weighted average interest rates | 0.4 | % |  | 0.2 | % |  | 0.4 | % |  | 0.3 | % |  | N/A |  | 0.1 | %
Nine Months Ended September 30 |  |  |  |  |  |  |  |  |  |  |
Maximum amount outstanding (based on daily outstanding balances) |  | $181.2 |  |  |  | $353.8 |  |  |  | $18.4 |  |  |  | $38.0 |  |  | $— |  |  | $204.7 |
Average amount outstanding (based on daily outstanding balances) |  | $114.5 |  |  |  | $281.9 |  |  |  | $0.2 |  |  |  | $0.3 |  |  | $— |  |  | $157.5 |
Weighted average interest rates | 0.4 | % |  | 0.2 | % |  | 0.4 | % |  | 0.2 | % |  | N/A |  | 0.1 | %

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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 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 19 -Article 5 + Details
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