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Income Taxes (Summary Of Tax Credit Carryforwards) (Details) $ in Millions | Mar. 31, 2018 USD ($)
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Federal [Member] |
Carryforwards [Line Items] |
Net operating losses, carryforward amount | $ 774
Tax credits, carryforward amount | 277
Federal [Member] | IPL [Member] |
Carryforwards [Line Items] |
Net operating losses, carryforward amount | 497
Tax credits, carryforward amount | 123
Federal [Member] | WPL [Member] |
Carryforwards [Line Items] |
Net operating losses, carryforward amount | 176
Tax credits, carryforward amount | 136
State [Member] |
Carryforwards [Line Items] |
Net operating losses, carryforward amount | 707
State [Member] | IPL [Member] |
Carryforwards [Line Items] |
Net operating losses, carryforward amount | 13
State [Member] | WPL [Member] |
Carryforwards [Line Items] |
Net operating losses, carryforward amount | $ 2

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- Definition Amount of operating loss carryforward, before tax effects, available to reduce future taxable income under enacted tax laws. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32559-109319 + Details
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- Definition The amount of the tax credit carryforward, before tax effects, available to reduce future taxable income under enacted tax laws. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32559-109319 + Details
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