XML 67 R52.htm IDEA: XBRL DOCUMENT
v2.4.0.8

Summary Of Significant Accounting Policies (Narrative) (Details) (USD $) In Millions, unless otherwise specified | 12 Months Ended
--- | ---
Dec. 31, 2013 | Dec. 31, 2012 | Dec. 31, 2011
Other Comprehensive Income: |  |  |
Other comprehensive income | $ 0.6 | $ 0 | $ 0.6
IPL [Member] |  |  |
General: |  |  |
Generation and distribution of steam, number of customers served (in customers) | 2 |  |
Operating Revenues: |  |  |
Estimated recovery of overaccrued operating revenue, reflected on customer billing, maximum period | 2 years |  |
WPL [Member] |  |  |
Operating Revenues: |  |  |
Final settlement recovery of overaccrued operating revenue, reflected on customer billing, maximum period | 2 years |  |
Sheboygan Falls Energy Facility [Member] |  |  |
General: |  |  |
Fossil-fueled EGU capacity (in megawatts) | 347 |  |
Capital lease, lease term | 20 years |  |
Franklin County Wind Project [Member] |  |  |
General: |  |  |
Wind EGU capacity (in megawatts) | 99 |  |

X
- Definition Capital Leases, Lease Term + References No definition available. + Details
Name: | lnt_CapitalLeasesLeaseTerm
Namespace Prefix: | lnt_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Electric Capacity Of Wind Project + References No definition available. + Details
Name: | lnt_ElectricCapacityOfWindProject
Namespace Prefix: | lnt_
Data Type: | num:powerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Estimated Recovery of Overaccrued Operating Revenue, Reflected on Customer Billing, Maximum Period + References No definition available. + Details
Name: | lnt_EstimatedRecoveryOfOveraccruedOperatingRevenueReflectedOnCustomerBillingMaximumPeriod
Namespace Prefix: | lnt_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Final Settlement Recovery of Overaccrued Operating Revenue, Reflected on Customer Billing, Maximum Period + References No definition available. + Details
Name: | lnt_FinalSettlementRecoveryOfOveraccruedOperatingRevenueReflectedOnCustomerBillingMaximumPeriod
Namespace Prefix: | lnt_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Fossil Fueled Energy Generating Units Capacity + References No definition available. + Details
Name: | lnt_FossilFueledEnergyGeneratingUnitsCapacity
Namespace Prefix: | lnt_
Data Type: | num:powerItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | lnt_GeneralAbstract
Namespace Prefix: | lnt_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Generation and Distribution of Steam, Number of Customers Served + References No definition available. + Details
Name: | lnt_GenerationAndDistributionOfSteamNumberOfCustomersServed
Namespace Prefix: | lnt_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount after tax of other comprehensive income (loss) attributable to parent entity. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 45 -Paragraph 20 -URI http://asc.fasb.org/extlink&oid=7656940&loc=SL4569643-111683 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 45 -Paragraph 19 -URI http://asc.fasb.org/extlink&oid=7656940&loc=SL4569616-111683 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 50 -Paragraph 1A -Subparagraph (c)(3) -URI http://asc.fasb.org/extlink&oid=18733093&loc=SL4573702-111684 + Details
Name: | us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | us-gaap_RevenuesAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration