XML 46 R118.htm IDEA: XBRL DOCUMENT v2.4.1.9

Benefit Plans (Recognized Compensation Expense And Income Tax Benefits) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Compensation expense	$ 15.3us-gaap_AllocatedShareBasedCompensationExpense	$ 12.0us-gaap_AllocatedShareBasedCompensationExpense	$ 6.9us-gaap_AllocatedShareBasedCompensationExpense
Income tax benefits	6.2us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense	4.8us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense	2.8us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense
IPL [Member]
Compensation expense	8.3us-gaap_AllocatedShareBasedCompensationExpense / dei_LegalEntityAxis = lnt_IplMember	6.2us-gaap_AllocatedShareBasedCompensationExpense / dei_LegalEntityAxis = lnt_IplMember	3.6us-gaap_AllocatedShareBasedCompensationExpense / dei_LegalEntityAxis = lnt_IplMember
Income tax benefits	3.4us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense / dei_LegalEntityAxis = lnt_IplMember	2.5us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense / dei_LegalEntityAxis = lnt_IplMember	1.5us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense / dei_LegalEntityAxis = lnt_IplMember
WPL [Member]
Compensation expense	6.4us-gaap_AllocatedShareBasedCompensationExpense / dei_LegalEntityAxis = lnt_WplMember	5.2us-gaap_AllocatedShareBasedCompensationExpense / dei_LegalEntityAxis = lnt_WplMember	3.0us-gaap_AllocatedShareBasedCompensationExpense / dei_LegalEntityAxis = lnt_WplMember
Income tax benefits	$ 2.6us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense / dei_LegalEntityAxis = lnt_WplMember	$ 2.1us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense / dei_LegalEntityAxis = lnt_WplMember	$ 1.2us-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

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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

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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: