XML 133 R119.htm IDEA: XBRL DOCUMENT
v2.4.1.9

Benefit Plans (Summary Of Performance Shares Activity) (Details) (Performance Shares [Member], USD $) In Millions, except Share data, unless otherwise specified | 12 Months Ended
--- | ---
Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward] |  |  |  |  |  |
Nonvested, January 1 (in shares/awards) | 139,940 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber | [1] | 145,277 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber | [1] | 236,979 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber | [1]
Granted (in shares) | 51,221 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod | [1] | 49,093 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod | [1] | 45,612 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod | [1]
Vested (in shares) | (45,235)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod | [1] | (54,430)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod | [1] | (111,980)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod | [1]
Forfeited (in shares) | (1,502)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod | [1],[2] | 0 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod | [1],[2] | (25,334)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod | [1],[2]
Nonvested, December 31 (in shares/awards) | 144,424 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber | [1] | 139,940 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber | [1] | 145,277 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber | [1]
Instrument valuation based on shares of common stock, number of shares | 1 lnt_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsInstrumentValuationBasedOnSharesOfCommonStockNumberOfShares |  |  |  |  |
Actual number of shares paid out upon vesting, minimum percentage of target shares | 0.00%lnt_ActualNumberOfSharesPaidOutUponVestingMinimum |  |  |  |  |
Actual number of shares paid out upon vesting, maximum percentage of target shares | 200.00%lnt_ActualNumberOfSharesPaidOutUponVestingMaximum |  |  |  |  |
2011 Grant [Member] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward] |  |  |  |  |  |
Vested (in shares) | (45,235)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod / us-gaap_AwardDateAxis = lnt_TwoThousandElevenGrantMember / us-gaap_AwardTypeAxis = us-gaap_PerformanceSharesMember |  |  |  |  |
Vested percentage of the target | 147.50%lnt_VestedPercentageOfTarget / us-gaap_AwardDateAxis = lnt_TwoThousandElevenGrantMember / us-gaap_AwardTypeAxis = us-gaap_PerformanceSharesMember |  |  |  |  |
Cash and stock payout value | 3.4 us-gaap_EmployeeBenefitsAndShareBasedCompensation / us-gaap_AwardDateAxis = lnt_TwoThousandElevenGrantMember / us-gaap_AwardTypeAxis = us-gaap_PerformanceSharesMember |  |  |  |  |
Cash payout value | 2.9 us-gaap_EmployeeServiceShareBasedCompensationCashFlowEffectCashUsedToSettleAwards / us-gaap_AwardDateAxis = lnt_TwoThousandElevenGrantMember / us-gaap_AwardTypeAxis = us-gaap_PerformanceSharesMember |  |  |  |  |
Common stock shares from vested performance shares (in shares) | 4,810 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod / us-gaap_AwardDateAxis = lnt_TwoThousandElevenGrantMember / us-gaap_AwardTypeAxis = us-gaap_PerformanceSharesMember |  |  |  |  |
2010 Grant [Member] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward] |  |  |  |  |  |
Vested (in shares) |  |  | (54,430)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod / us-gaap_AwardDateAxis = lnt_TwoThousandTenGrantMember / us-gaap_AwardTypeAxis = us-gaap_PerformanceSharesMember |  |  |
Vested percentage of the target |  |  | 197.50%lnt_VestedPercentageOfTarget / us-gaap_AwardDateAxis = lnt_TwoThousandTenGrantMember / us-gaap_AwardTypeAxis = us-gaap_PerformanceSharesMember |  |  |
Cash and stock payout value |  |  | 4.8 us-gaap_EmployeeBenefitsAndShareBasedCompensation / us-gaap_AwardDateAxis = lnt_TwoThousandTenGrantMember / us-gaap_AwardTypeAxis = us-gaap_PerformanceSharesMember |  |  |
Cash payout value |  |  | 4.4 us-gaap_EmployeeServiceShareBasedCompensationCashFlowEffectCashUsedToSettleAwards / us-gaap_AwardDateAxis = lnt_TwoThousandTenGrantMember / us-gaap_AwardTypeAxis = us-gaap_PerformanceSharesMember |  |  |
Common stock shares from vested performance shares (in shares) |  |  | 4,177 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod / us-gaap_AwardDateAxis = lnt_TwoThousandTenGrantMember / us-gaap_AwardTypeAxis = us-gaap_PerformanceSharesMember |  |  |
2009 Grant [Member] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward] |  |  |  |  |  |
Vested (in shares) |  |  |  |  | (111,980)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod / us-gaap_AwardDateAxis = lnt_TwoThousandNineGrantMember / us-gaap_AwardTypeAxis = us-gaap_PerformanceSharesMember |
Vested percentage of the target |  |  |  |  | 162.50%lnt_VestedPercentageOfTarget / us-gaap_AwardDateAxis = lnt_TwoThousandNineGrantMember / us-gaap_AwardTypeAxis = us-gaap_PerformanceSharesMember |
Cash and stock payout value |  |  |  |  | 8.0 us-gaap_EmployeeBenefitsAndShareBasedCompensation / us-gaap_AwardDateAxis = lnt_TwoThousandNineGrantMember / us-gaap_AwardTypeAxis = us-gaap_PerformanceSharesMember |
Cash payout value |  |  |  |  | 7.8 us-gaap_EmployeeServiceShareBasedCompensationCashFlowEffectCashUsedToSettleAwards / us-gaap_AwardDateAxis = lnt_TwoThousandNineGrantMember / us-gaap_AwardTypeAxis = us-gaap_PerformanceSharesMember |
Common stock shares from vested performance shares (in shares) |  |  |  |  | 6,399 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod / us-gaap_AwardDateAxis = lnt_TwoThousandNineGrantMember / us-gaap_AwardTypeAxis = us-gaap_PerformanceSharesMember |
[1] | Share amounts represent the target number of performance shares. Each performance share’s value is based on the closing market price of one share of Alliant Energy’s common stock at the end of the performance period. The actual number of shares that will be paid out upon vesting is dependent upon actual performance and may range from zero to 200% of the target number of shares.
[2] | Forfeitures were primarily caused by retirements and voluntary terminations of participants.

X
- Definition Actual Number Of Shares Paid Out Upon Vesting Maximum + References No definition available. + Details
Name: | lnt_ActualNumberOfSharesPaidOutUponVestingMaximum
Namespace Prefix: | lnt_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Actual Number Of Shares Paid Out Upon Vesting Minimum + References No definition available. + Details
Name: | lnt_ActualNumberOfSharesPaidOutUponVestingMinimum
Namespace Prefix: | lnt_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Instrument Valuation Based On Shares of Common Stock, Number of Shares + References No definition available. + Details
Name: | lnt_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsInstrumentValuationBasedOnSharesOfCommonStockNumberOfShares
Namespace Prefix: | lnt_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition Vested Percentage Of The Target + References No definition available. + Details
Name: | lnt_VestedPercentageOfTarget
Namespace Prefix: | lnt_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Costs and payments related to employee benefits and equity-based compensation, such as pension expense and contributions, other postretirement benefits expense and payments, stock or unit options expense, and amortization of restricted stock or unit. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 + Details
Name: | us-gaap_EmployeeBenefitsAndShareBasedCompensation
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Aggregate cash paid by the entity during the period to settle equity instruments granted under equity-based payment arrangements. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (k) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
Name: | us-gaap_EmployeeServiceShareBasedCompensationCashFlowEffectCashUsedToSettleAwards
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(iv)(3) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(i)-(ii) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

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

X
- Definition The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(2) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of share instruments newly issued under a share-based compensation plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_AwardDateAxis=lnt_TwoThousandElevenGrantMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AwardDateAxis=lnt_TwoThousandNineGrantMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AwardDateAxis=lnt_TwoThousandTenGrantMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |