v2.4.0.6

Debt (Long-term Debt) (Details) (USD $) In Millions, unless otherwise specified | 12 Months Ended |
--- | --- | ---
Dec. 31, 2012 | Dec. 31, 2011
Debt Instrument [Line Items] |  |  |  |
Long-term debt, carrying value | $ 3,149.9 |  | $ 2,716.3 |
Commercial paper | 217.5 |  | 102.8 |
Current maturities | (1.5) |  | (1.4) |
Unamortized debt (discount) and premium, net | (11.8) |  | (11.8) |
Long-term debt, net | 3,136.6 |  | 2,703.1 |
Remaining maturity | 8 days |  |  |
Senior Debentures [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt, carrying value | 1,275.0 |  | 1,275.0 |
Senior Debentures [Member] | 3.3% senior debenture due 2015 [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt, carrying value | 150.0 |  | 150.0 |
Interest rate | 3.30% |  |  |
Senior Debentures [Member] | 5.875% senior debenture due 2018 [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt, carrying value | 100.0 |  | 100.0 |
Interest rate | 5.875% |  |  |
Senior Debentures [Member] | 7.25% senior debenture due 2018 [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt, carrying value | 250.0 |  | 250.0 |
Interest rate | 7.25% |  |  |
Senior Debentures [Member] | 3.65% senior debenture due 2020 [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt, carrying value | 200.0 |  | 200.0 |
Interest rate | 3.65% |  |  |
Senior Debentures [Member] | 5.5% senior debenture due 2025 [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt, carrying value | 50.0 |  | 50.0 |
Interest rate | 5.50% |  |  |
Senior Debentures [Member] | 6.45% senior debenture due 2033 [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt, carrying value | 100.0 |  | 100.0 |
Interest rate | 6.45% |  |  |
Senior Debentures [Member] | 6.3% senior debenture due 2034 [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt, carrying value | 125.0 |  | 125.0 |
Interest rate | 6.30% |  |  |
Senior Debentures [Member] | 6.25% senior debenture due 2039 [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt, carrying value | 300.0 |  | 300.0 |
Interest rate | 6.25% |  |  |
Debentures [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt, carrying value | 1,300.0 |  | 1,050.0 |
Debentures [Member] | 5% debenture due 2019 [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt, carrying value | 250.0 |  | 250.0 |
Interest rate | 5.00% |  |  |
Debentures [Member] | 4.6% debenture due 2020 [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt, carrying value | 150.0 |  | 150.0 |
Interest rate | 4.60% |  |  |
Debentures [Member] | 2.25% debenture due 2022 [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt, carrying value | 250.0 | [1] | 0 | [1]
Interest rate | 2.25% |  |  |
Debentures [Member] | 6.25% debenture due 2034 [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt, carrying value | 100.0 |  | 100.0 |
Interest rate | 6.25% |  |  |
Debentures [Member] | 6.375% debenture due 2037 [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt, carrying value | 300.0 |  | 300.0 |
Interest rate | 6.375% |  |  |
Debentures [Member] | 7.6% debenture due 2038 [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt, carrying value | 250.0 |  | 250.0 |
Interest rate | 7.60% |  |  |
Pollution Control Revenue Bonds [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt, carrying value | 77.5 |  | 77.5 |
Pollution Control Revenue Bonds [Member] | 5% pollution control revenue bond due 2014 [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt, carrying value | 38.4 |  | 38.4 |
Interest rate | 5.00% |  |  |
Pollution Control Revenue Bonds [Member] | 5% pollution control revenue bond due 2014 and 2015 [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt, carrying value | 24.5 |  | 24.5 |
Interest rate | 5.00% |  |  |
Pollution Control Revenue Bonds [Member] | 5.375% pollution control revenue bond due 2015 [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt, carrying value | 14.6 |  | 14.6 |
Interest rate | 5.375% |  |  |
Other Long Term Debt [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt, carrying value | 497.4 |  | 313.8 |
Long-term debt [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Commercial paper | 50.0 | [2] | 0 | [2]
Interest rate | 0.40% |  |  |
Senior Notes [Member] | 4% senior notes, due 2014 [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt, carrying value | 250.0 |  | 250.0 |
Interest rate | 4.00% |  |  |
Senior Notes [Member] | 3.45% senior notes, due 2022 [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt, carrying value | 75.0 | [3] | 0 | [3]
Interest rate | 3.45% |  |  |
Term Loan Credit Agreement [Member] | Term loan credit agreement through 2014, 1.1% at December 31, 2012 [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt, carrying value | 60.0 | [4] | 0 | [4]
Interest rate | 1.10% |  |  |
Senior Secured Notes [Member] | 5.06% senior secured notes, due 2013 to 2024 [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt, carrying value | 61.9 |  | 63.3 |
Interest rate | 5.06% |  |  |
Other [Member] | Other, 1% at December 31, 2012, due 2013 to 2025 [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt, carrying value | 0.5 |  | 0.5 |
Interest rate | 1.00% |  |  |
IPL [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt, carrying value | 1,363.4 |  | 1,313.4 |
Commercial paper | 26.3 |  | 7.1 |
Current maturities | 0 |  | 0 |
Unamortized debt (discount) and premium, net | (3.9) |  | (4.4) |
Long-term debt, net | 1,359.5 |  | 1,309.0 |
IPL [Member] | Senior Debentures [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt, carrying value | 1,275.0 |  | 1,275.0 |
IPL [Member] | Senior Debentures [Member] | 3.3% senior debenture due 2015 [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt, carrying value | 150.0 |  | 150.0 |
Interest rate | 3.30% |  |  |
IPL [Member] | Senior Debentures [Member] | 5.875% senior debenture due 2018 [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt, carrying value | 100.0 |  | 100.0 |
Interest rate | 5.875% |  |  |
IPL [Member] | Senior Debentures [Member] | 7.25% senior debenture due 2018 [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt, carrying value | 250.0 |  | 250.0 |
Interest rate | 7.25% |  |  |
IPL [Member] | Senior Debentures [Member] | 3.65% senior debenture due 2020 [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt, carrying value | 200.0 |  | 200.0 |
Interest rate | 3.65% |  |  |
IPL [Member] | Senior Debentures [Member] | 5.5% senior debenture due 2025 [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt, carrying value | 50.0 |  | 50.0 |
Interest rate | 5.50% |  |  |
IPL [Member] | Senior Debentures [Member] | 6.45% senior debenture due 2033 [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt, carrying value | 100.0 |  | 100.0 |
Interest rate | 6.45% |  |  |
IPL [Member] | Senior Debentures [Member] | 6.3% senior debenture due 2034 [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt, carrying value | 125.0 |  | 125.0 |
Interest rate | 6.30% |  |  |
IPL [Member] | Senior Debentures [Member] | 6.25% senior debenture due 2039 [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt, carrying value | 300.0 |  | 300.0 |
Interest rate | 6.25% |  |  |
IPL [Member] | Pollution Control Revenue Bonds [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt, carrying value | 38.4 |  | 38.4 |
IPL [Member] | Pollution Control Revenue Bonds [Member] | 5% pollution control revenue bond due 2014 [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt, carrying value | 38.4 |  | 38.4 |
Interest rate | 5.00% |  |  |
IPL [Member] | Other Long Term Debt [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt, carrying value | 50.0 |  | 0 |
IPL [Member] | Long-term debt [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Commercial paper | 50.0 | [2] | 0 | [2]
Interest rate | 0.40% |  |  |
WPL [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt, carrying value | 1,339.1 |  | 1,089.1 |
Commercial paper | 86.6 |  | 25.7 |
Current maturities | 0 |  | 0 |
Unamortized debt (discount) and premium, net | (7.6) |  | (6.9) |
Long-term debt, net | 1,331.5 |  | 1,082.2 |
WPL [Member] | Debentures [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt, carrying value | 1,300.0 |  | 1,050.0 |
WPL [Member] | Debentures [Member] | 5% debenture due 2019 [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt, carrying value | 250.0 |  | 250.0 |
Interest rate | 5.00% |  |  |
WPL [Member] | Debentures [Member] | 4.6% debenture due 2020 [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt, carrying value | 150.0 |  | 150.0 |
Interest rate | 4.60% |  |  |
WPL [Member] | Debentures [Member] | 2.25% debenture due 2022 [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt, carrying value | 250.0 | [1] | 0 | [1]
Interest rate | 2.25% |  |  |
WPL [Member] | Debentures [Member] | 6.25% debenture due 2034 [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt, carrying value | 100.0 |  | 100.0 |
Interest rate | 6.25% |  |  |
WPL [Member] | Debentures [Member] | 6.375% debenture due 2037 [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt, carrying value | 300.0 |  | 300.0 |
Interest rate | 6.375% |  |  |
WPL [Member] | Debentures [Member] | 7.6% debenture due 2038 [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt, carrying value | 250.0 |  | 250.0 |
Interest rate | 7.60% |  |  |
WPL [Member] | Pollution Control Revenue Bonds [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt, carrying value | 39.1 |  | 39.1 |
WPL [Member] | Pollution Control Revenue Bonds [Member] | 5% pollution control revenue bond due 2014 and 2015 [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt, carrying value | 24.5 |  | 24.5 |
Interest rate | 5.00% |  |  |
WPL [Member] | Pollution Control Revenue Bonds [Member] | 5.375% pollution control revenue bond due 2015 [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt, carrying value | $ 14.6 |  | $ 14.6 |
Interest rate | 5.375% |  |  |
[1] | In 2012, WPL issued $250.0 million of 2.25% debentures due 2022. The proceeds from the issuance were used by WPL to fund a portion of the purchase price of Riverside.
[2] | As of December 31, 2012, $50.0 million of commercial paper was recorded in “Long-term debt, net” on Alliant Energy’s and IPL’s Consolidated Balance Sheets due to the existence of long-term credit facilities that back-stop this commercial paper balance, along with Alliant Energy’s and IPL’s intent and ability to refinance these balances on a long-term basis. As of December 31, 2012, this commercial paper balance had a remaining maturity of 8 days.
[3] | In 2012, Corporate Services issued $75 million of 3.45% senior notes due 2022. The proceeds from the issuance were used by Corporate Services to repay short-term debt primarily incurred for the purchase of the corporate headquarters building and for general working capital purposes.
[4] | In 2012, Franklin County Holdings LLC, Resources’ wholly-owned subsidiary, entered into a $60.0 million variable-rate term loan credit agreement that exists through 2014 to fund a portion of the costs of its Franklin County wind project, which was placed into service in the fourth quarter of 2012.

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- Definition Carrying value as of the balance sheet date of short-term borrowings using unsecured obligations issued by banks, corporations and other borrowers to investors. The maturities of these money market securities generally do not exceed 270 days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 19 -Subparagraph a(3) -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 13 -Subparagraph 2 -Article 9 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 16 -Article 7 Reference 4: 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(a)(3)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.13(2)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 + Details
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- Definition The amount of debt discount (net of debt premium) that was originally recognized at the issuance of the instrument that has yet to be amortized. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 21 -Paragraph 16 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28555-108399 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28567-108399 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 55 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=6584090&loc=d3e28878-108400 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 1A -URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28541-108399 Reference 7: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 21 -Paragraph 20 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. + Details
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- Definition Carrying amount of long-term debt, net of unamortized discount or premium, including current and noncurrent amounts. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.16) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 16 -Article 9 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 16 -Article 7 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 20, 22 -Article 5 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.16) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 + Details
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