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Valuation And Qualifying Accounts and Reserves (Details) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2015 | Dec. 31, 2014 | Dec. 31, 2013
Accumulated Provision for Uncollectible Accounts [Member] |  |  |  |
Valuation and Qualifying Accounts Disclosure [Line Items] |  |  |  |
Beginning Balance | [1] | $ 5.1 | $ 4.8 | $ 4.0
Charged to Expense | [1] | 8.1 | 11.7 | 13.6
Charged to Other Accounts | [1],[2] | 3.0 | 4.1 | 0.6
Deductions | [1],[3] | 11.4 | 15.5 | 13.4
Ending Balance | [1] | 4.8 | 5.1 | 4.8
Accumulated Provision for Uncollectible Accounts [Member] | IPL [Member] |  |  |  |
Valuation and Qualifying Accounts Disclosure [Line Items] |  |  |  |
Beginning Balance | [1] | 0.4 | 0.7 | 0.7
Charged to Expense | [1] | 8.1 | 11.5 | 12.7
Charged to Other Accounts | [1],[2] | 0.0 | 0.0 | 0.0
Deductions | [1],[3] | 7.9 | 11.8 | 12.7
Ending Balance | [1] | 0.6 | 0.4 | 0.7
Accumulated Provision for Uncollectible Accounts [Member] | WPL [Member] |  |  |  |
Valuation and Qualifying Accounts Disclosure [Line Items] |  |  |  |
Beginning Balance |  | 4.2 | 1.7 | 1.8
Charged to Expense |  | 0.0 | 0.0 | 0.0
Charged to Other Accounts | [2] | 3.0 | 4.1 | 0.6
Deductions | [3] | 3.5 | 1.6 | 0.7
Ending Balance |  | 3.7 | 4.2 | 1.7
Accumulated Provision for Other Reserves [Member] |  |  |  |
Valuation and Qualifying Accounts Disclosure [Line Items] |  |  |  |
Beginning Balance | [4] | 32.6 | 38.2 | 33.4
Charged to Expense | [4] | 6.5 | 12.5 | 23.2
Charged to Other Accounts | [2],[4] | 0.0 | 0.0 | 0.0
Deductions | [3],[4] | 12.0 | 18.1 | 18.4
Ending Balance | [4] | 27.1 | 32.6 | 38.2
Accumulated Provision for Other Reserves [Member] | IPL [Member] |  |  |  |
Valuation and Qualifying Accounts Disclosure [Line Items] |  |  |  |
Beginning Balance | [4] | 10.6 | 18.1 | 11.6
Charged to Expense | [4] | 2.1 | 3.9 | 9.3
Charged to Other Accounts | [2],[4] | 0.0 | 0.0 | 0.0
Deductions | [3],[4] | 3.3 | 11.4 | 2.8
Ending Balance | [4] | 9.4 | 10.6 | 18.1
Accumulated Provision for Other Reserves [Member] | WPL [Member] |  |  |  |
Valuation and Qualifying Accounts Disclosure [Line Items] |  |  |  |
Beginning Balance | [4] | 16.3 | 16.2 | 13.5
Charged to Expense | [4] | 0.7 | 2.5 | 8.8
Charged to Other Accounts | [2],[4] | 0.0 | 0.0 | 0.0
Deductions | [3],[4] | 5.6 | 2.4 | 6.1
Ending Balance | [4] | $ 11.4 | $ 16.3 | $ 16.2
[1] | Refer to Note 5(b) for discussion of IPL’s sales of accounts receivable program.
[2] | Accumulated provision for uncollectible accounts: In accordance with its regulatory treatment, certain amounts provided by WPL are recorded in regulatory assets.
[3] | Deductions are of the nature for which the reserves were created. In the case of the accumulated provision for uncollectible accounts, deductions from this reserve are reduced by recoveries of amounts previously written off.
[4] | Other reserves are largely related to injury and damage claims arising in the ordinary course of business.

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- Definition Total of allowances and reserves, the valuation and qualifying accounts that are either netted against the cost of an asset (in order to value it at its carrying value) or that reflect a liability established to represent expected future costs. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24092-122690 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 09 -Article 12 + Details
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