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Summary Of Significant Accounting Policies (Schedule Of Average Rates Of Depreciation) (Details) | 12 Months Ended
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Dec. 31, 2015 | Dec. 31, 2014 | Dec. 31, 2013
Electric - generation [Member] | IPL [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Average rate of depreciation | 3.60% | 3.60% | 3.60%
Electric - generation [Member] | WPL [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Average rate of depreciation | 3.20% | 3.20% | 3.30%
Electric - distribution [Member] | IPL [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Average rate of depreciation | 2.40% | 2.50% | 2.50%
Electric - distribution [Member] | WPL [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Average rate of depreciation | 2.70% | 2.70% | 2.70%
Electric - other [Member] | IPL [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Average rate of depreciation | 4.00% | 4.00% | 4.00%
Electric - other [Member] | WPL [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Average rate of depreciation | 4.50% | 5.90% | 5.00%
Gas [Member] | IPL [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Average rate of depreciation | 3.20% | 3.30% | 3.40%
Gas [Member] | WPL [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Average rate of depreciation | 2.50% | 2.50% | 2.50%
Other [Member] | IPL [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Average rate of depreciation | 3.90% | 4.30% | 4.70%
Other [Member] | WPL [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Average rate of depreciation | 6.00% | 6.00% | 5.10%

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- Definition Composite depreciation rate for public utility plants in service. + References No definition available. + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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