v2.4.0.6

Debt (Tables) | 9 Months Ended
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Sep. 30, 2012
Debt Disclosure [Abstract] |
Credit Facilities | Information regarding commercial paper issued under Alliant Energy’s, IPL’s and WPL’s credit facilities classified as short-term debt was as follows (dollars in millions):
| Alliant Energy |  | Parent |  |  |  |
September 30, 2012 | (Consolidated) |  | Company |  | IPL |  | WPL
Commercial paper: |  |  |  |  |  |  |
Amount outstanding | $70.4 |  | $70.4 |  | $— |  | $—
Remaining maturity | 1 day |  | 1 day |  | N/A |  | N/A
Interest rates | 0.4% |  | 0.4% |  | N/A |  | N/A
Available credit facility capacity (a) | $879.6 |  | $229.6 |  | $250.0 |  | $400.0
Other Short-Term Borrowings |
| Alliant Energy |  | IPL |  | WPL
Three Months Ended September 30 | 2012 |  | 2011 |  | 2012 |  | 2011 |  | 2012 |  | 2011
Maximum amount outstanding (based on daily outstanding balances) |  | $185.3 |  |  |  | $22.1 |  |  |  | $19.5 |  |  |  | $18.0 |  |  |  | $35.6 |  |  |  | $— |
Average amount outstanding (based on daily outstanding balances) |  | $133.0 |  |  |  | $2.6 |  |  |  | $1.3 |  |  |  | $1.7 |  |  |  | $11.9 |  |  |  | $— |
Weighted average interest rates | 0.4 | % |  | 0.4 | % |  | 0.4 | % |  | 0.3 | % |  | 0.3 | % |  | N/A |
Nine Months Ended September 30 |  |  |  |  |  |  |  |  |  |  |
Maximum amount outstanding (based on daily outstanding balances) |  | $185.3 |  |  |  | $96.5 |  |  |  | $35.4 |  |  |  | $54.4 |  |  |  | $35.6 |  |  |  | $96.5 |
Average amount outstanding (based on daily outstanding balances) |  | $100.2 |  |  |  | $28.7 |  |  |  | $7.2 |  |  |  | $7.1 |  |  |  | $13.3 |  |  |  | $23.0 |
Weighted average interest rates | 0.4 | % |  | 0.3 | % |  | 0.4 | % |  | 0.3 | % |  | 0.3 | % |  | 0.3 | %
(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, 2012. Refer to Note 7(b) for further discussion of $50 million of commercial paper outstanding at September 30, 2012 classified as long-term debt.

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- Definition Tabular disclosure of short-term or long-term contractual arrangements with lenders, including letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. + 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(b),22(b)) -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 -Article 4 -Section 08 -Paragraph f Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 19, 22 -Article 5 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08.(e),(f)) -URI http://asc.fasb.org/extlink&oid=6881521&loc=d3e23780-122690 + Details
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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 SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 19 -Article 5 Reference 2: 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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