XML 88 R60.htm IDEA: XBRL DOCUMENT
v2.4.1.9

Benefit Plans (Recognized Compensation Expense And Income Tax Benefits) (Details) (USD $) In Millions, unless otherwise specified | 3 Months Ended
--- | ---
Mar. 31, 2015 | Mar. 31, 2014
Compensation expense | $ 3.2 us-gaap_AllocatedShareBasedCompensationExpense | $ 3.1 us-gaap_AllocatedShareBasedCompensationExpense
Income tax benefits | 1.3 us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense | 1.3 us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense
IPL [Member] |  |
Compensation expense | 1.7 us-gaap_AllocatedShareBasedCompensationExpense / dei_LegalEntityAxis = lnt_IplMember | 1.7 us-gaap_AllocatedShareBasedCompensationExpense / dei_LegalEntityAxis = lnt_IplMember
Income tax benefits | 0.7 us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense / dei_LegalEntityAxis = lnt_IplMember | 0.7 us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense / dei_LegalEntityAxis = lnt_IplMember
WPL [Member] |  |
Compensation expense | 1.4 us-gaap_AllocatedShareBasedCompensationExpense / dei_LegalEntityAxis = lnt_WplMember | 1.3 us-gaap_AllocatedShareBasedCompensationExpense / dei_LegalEntityAxis = lnt_WplMember
Income tax benefits | $ 0.6 us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense / dei_LegalEntityAxis = lnt_WplMember | $ 0.5 us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense / dei_LegalEntityAxis = lnt_WplMember

X
- Definition Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5047-113901 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 14.F) -URI http://asc.fasb.org/extlink&oid=27013229&loc=d3e301413-122809 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (h)(1)(i) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 14 -Section F + Details
Name: | us-gaap_AllocatedShareBasedCompensationExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The total recognized tax benefit related to compensation cost for equity-based payment arrangements recognized in income during the 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 (h)(1)(i) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
Name: | us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | dei_LegalEntityAxis=lnt_IplMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=lnt_WplMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |