XML 128 R51.htm IDEA: XBRL DOCUMENT v2.4.0.8

Income Taxes Income Taxes (IPL's Tax Benefit Riders) (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
IPL's Tax Benefit Riders [Line Items]
Income tax rates for continuing operations	13.30%	19.50%	13.00%	28.30%
Tax Benefit Rider [Member]
IPL's Tax Benefit Riders [Line Items]
Income tax rates for continuing operations	(11.70%)	(11.70%)	(12.30%)	(11.90%)
IPL [Member]
IPL's Tax Benefit Riders [Line Items]
Income tax rates for continuing operations	(24.70%)	(12.00%)	(24.30%)	22.60%
IPL [Member] | Tax Benefit Rider [Member]
IPL's Tax Benefit Riders [Line Items]
Income tax rates for continuing operations	(33.30%)	(34.90%)	(35.60%)	(35.50%)

X

- Details

Name:	lnt_IplsTaxBenefitRidersLineItems
Namespace Prefix:	lnt_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

A ratio calculated by dividing the reported amount of income tax expense attributable to continuing operations for the period by GAAP-basis pretax income from continuing operations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

-Section 50

-Paragraph 12

-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32687-109319



Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

-Section 50

-Paragraph 13

-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32698-109319



Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.4-08.(h)(2))

-URI http://asc.fasb.org/extlink&oid=6881521&loc=d3e23780-122690



Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 08

-Paragraph h

-Subparagraph 2

-Article 4



Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 109

-Paragraph 47

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Name:	us-gaap_EffectiveIncomeTaxRateContinuingOperations
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration