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Debt (Schedule Of Debt Maturities) (Details) (USD $) In Millions, unless otherwise specified | Dec. 31, 2014
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2015 | $ 183 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths
2016 | 313 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo
2017 | 5 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree
2018 | 356 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour
2019 | 256 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive
IPL [Member] |
2015 | 150 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths / dei_LegalEntityAxis = lnt_IplMember
2016 | 0 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo / dei_LegalEntityAxis = lnt_IplMember
2017 | 0 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree / dei_LegalEntityAxis = lnt_IplMember
2018 | 350 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour / dei_LegalEntityAxis = lnt_IplMember
2019 | 0 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive / dei_LegalEntityAxis = lnt_IplMember
WPL [Member] |
2015 | 31 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths / dei_LegalEntityAxis = lnt_WplMember
2016 | 0 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo / dei_LegalEntityAxis = lnt_WplMember
2017 | 0 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree / dei_LegalEntityAxis = lnt_WplMember
2018 | 0 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour / dei_LegalEntityAxis = lnt_WplMember
2019 | 250 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive / dei_LegalEntityAxis = lnt_WplMember
Resources [Member] |
2015 | 2 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths / dei_LegalEntityAxis = lnt_ResourcesMember
2016 | 63 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo / dei_LegalEntityAxis = lnt_ResourcesMember
2017 | 5 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree / dei_LegalEntityAxis = lnt_ResourcesMember
2018 | 6 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour / dei_LegalEntityAxis = lnt_ResourcesMember
2019 | 6 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive / dei_LegalEntityAxis = lnt_ResourcesMember
Alliant Energy Parent Company [Member] |
2015 | 0 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
2016 | 250 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
2017 | 0 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
2018 | 0 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
2019 | $ 0 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive / dei_LegalEntityAxis = us-gaap_ParentCompanyMember

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- Definition Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6802200&loc=d3e1835-112601 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-04.(a)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24072-122690 + Details
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- Definition Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6802200&loc=d3e1835-112601 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-04.(a)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24072-122690 + Details
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- Definition Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the third fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6802200&loc=d3e1835-112601 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-04.(a)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24072-122690 + Details
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