v2.4.0.6

Benefit Plans (Amounts Recognized On The Consolidated Balance Sheets) (Details) (USD $) In Millions, unless otherwise specified | Dec. 31, 2012 | Dec. 31, 2011
--- | --- | ---
Amounts recognized on the Consolidated Balance Sheets consist of: |  |  |  |
Pension and other benefit obligations | $ (364.0) |  | $ (312.7) |
Amounts recognized in Regulatory Assets, Regulatory Liabilities and AOCL consist of (b): |  |  |  |
Regulatory liability recognized related to other postretirement benefit plans | 2.7 |  | 3.3 |
Pension Plans, Defined Benefit [Member] |  |  |  |
Amounts recognized on the Consolidated Balance Sheets consist of: |  |  |  |
Non-current assets | 0 |  | 0 |
Other current liabilities | (2.4) |  | (4.6) |
Pension and other benefit obligations | (239.5) |  | (179.4) |
Net amount recognized at December 31 | (241.9) |  | (184.0) |
Amounts recognized in Regulatory Assets, Regulatory Liabilities and AOCL consist of (b): |  |  |  |
Net actuarial loss | 533.4 | [1] | 494.8 | [1]
Prior service credit | (7.2) | [1] | (6.9) | [1]
Net amount recognized at December 31 | 526.2 | [1] | 487.9 | [1]
Other Postretirement Benefits Plans [Member] |  |  |  |
Amounts recognized on the Consolidated Balance Sheets consist of: |  |  |  |
Non-current assets | 3.5 |  | 1.3 |
Other current liabilities | (2.8) |  | 0 |
Pension and other benefit obligations | (100.8) |  | (105.1) |
Net amount recognized at December 31 | (100.1) |  | (103.8) |
Amounts recognized in Regulatory Assets, Regulatory Liabilities and AOCL consist of (b): |  |  |  |
Net actuarial loss | 62.1 | [1] | 76.7 | [1]
Prior service credit | (40.5) | [1] | (52.5) | [1]
Net amount recognized at December 31 | 21.6 | [1] | 24.2 | [1]
IPL [Member] |  |  |  |
Amounts recognized on the Consolidated Balance Sheets consist of: |  |  |  |
Pension and other benefit obligations | (122.9) |  | (101.9) |
Amounts recognized in Regulatory Assets, Regulatory Liabilities and AOCL consist of (b): |  |  |  |
Regulatory liability recognized related to other postretirement benefit plans | 1.4 |  | 2.8 |
IPL [Member] | Pension Plans, Defined Benefit [Member] |  |  |  |
Amounts recognized on the Consolidated Balance Sheets consist of: |  |  |  |
Pension and other benefit obligations | (66.1) |  | (45.8) |
Amounts recognized in Regulatory Assets, Regulatory Liabilities and AOCL consist of (b): |  |  |  |
Net actuarial loss | 149.7 | [2] | 141.1 | [2]
Prior service credit | 0.7 | [2] | 1.1 | [2]
Net amount recognized at December 31 | 150.4 | [2] | 142.2 | [2]
IPL [Member] | Other Postretirement Benefits Plans [Member] |  |  |  |
Amounts recognized on the Consolidated Balance Sheets consist of: |  |  |  |
Pension and other benefit obligations | (17.2) |  | (22.8) |
Amounts recognized in Regulatory Assets, Regulatory Liabilities and AOCL consist of (b): |  |  |  |
Net actuarial loss | 32.0 | [2] | 41.0 | [2]
Prior service credit | (21.3) | [2] | (27.6) | [2]
Net amount recognized at December 31 | 10.7 | [2] | 13.4 | [2]
WPL [Member] |  |  |  |
Amounts recognized on the Consolidated Balance Sheets consist of: |  |  |  |
Pension and other benefit obligations | (159.7) |  | (128.0) |
Amounts recognized in Regulatory Assets, Regulatory Liabilities and AOCL consist of (b): |  |  |  |
Regulatory liability recognized related to other postretirement benefit plans | 0.2 |  | 0 |
WPL [Member] | Pension Plans, Defined Benefit [Member] |  |  |  |
Amounts recognized on the Consolidated Balance Sheets consist of: |  |  |  |
Non-current assets | 0 |  | 0 |
Other current liabilities | 0 |  | 0 |
Pension and other benefit obligations | (67.0) |  | (42.9) |
Net amount recognized at December 31 | (67.0) |  | (42.9) |
Amounts recognized in Regulatory Assets, Regulatory Liabilities and AOCL consist of (b): |  |  |  |
Net actuarial loss | 155.3 | [3] | 142.7 | [3]
Prior service credit | 1.9 | [3] | 2.4 | [3]
Net amount recognized at December 31 | 157.2 | [3] | 145.1 | [3]
WPL [Member] | Other Postretirement Benefits Plans [Member] |  |  |  |
Amounts recognized on the Consolidated Balance Sheets consist of: |  |  |  |
Non-current assets | 3.5 |  | 1.3 |
Other current liabilities | (2.8) |  | 0 |
Pension and other benefit obligations | (67.5) |  | (65.8) |
Net amount recognized at December 31 | (66.8) |  | (64.5) |
Amounts recognized in Regulatory Assets, Regulatory Liabilities and AOCL consist of (b): |  |  |  |
Net actuarial loss | 24.3 | [3] | 27.8 | [3]
Prior service credit | (13.4) | [3] | (17.3) | [3]
Net amount recognized at December 31 | $ 10.9 | [3] | $ 10.5 | [3]
[1] | Refer to Note 1(b) and Alliant Energy’s Consolidated Statements of Common Equity for amounts recognized in “Regulatory assets” and “AOCL,” respectively, on Alliant Energy’s Consolidated Balance Sheets. At December 31, 2012 and 2011, $2.7 million and $3.3 million, respectively, of regulatory liabilities were recognized related to Alliant Energy’s other postretirement benefits plans.
[2] | Refer to Note 1(b) for amounts recognized in “Regulatory assets” on IPL’s Consolidated Balance Sheets. At December 31, 2012 and 2011, $1.4 million and $2.8 million, respectively, of regulatory liabilities were recognized related to IPL’s other postretirement benefits plans.
[3] | Refer to Note 1(b) for amounts recognized in “Regulatory assets” on WPL’s Consolidated Balance Sheets. At December 31, 2012 and 2011, $0.2 million and $0, respectively, of regulatory liabilities were recognized related to WPL’s other postretirement benefits plans.

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- Definition The aggregate net amount recognized in the balance sheet associated with the defined benefit plan(s). Will normally be the same as the Defined Benefit Plan, Funded Status of Plan, Total. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 132R -Paragraph 5 -Subparagraph c -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 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=21915506&loc=d3e1928-114920 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=21915240&loc=d3e1703-114919 + Details
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