XML 27 R55.htm IDEA: XBRL DOCUMENT v3.2.0.727

Income Taxes (Schedule Of Effective Income Tax Rates) (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Effective Tax Rate [Line Items]
Statutory federal income tax rate	35.00%	35.00%	35.00%	35.00%
IPL's tax benefit riders	(10.60%)	(11.90%)	(10.20%)	(11.90%)
Effect of rate-making on property-related differences	(8.40%)	(4.80%)	(7.00%)	(5.10%)
Production tax credits	(6.50%)	(6.10%)	(6.40%)	(6.50%)
Other items, net	4.10%	4.80%	4.30%	4.70%
Overall income tax rate	13.60%	17.00%	15.70%	16.20%
IPL [Member]
Effective Tax Rate [Line Items]
Statutory federal income tax rate	35.00%	35.00%	35.00%	35.00%
IPL's tax benefit riders	(25.30%)	(36.60%)	(25.20%)	(32.80%)
Effect of rate-making on property-related differences	(22.30%)	(14.40%)	(16.60%)	(13.00%)
Production tax credits	(7.20%)	(8.00%)	(7.20%)	(8.20%)
Other items, net	4.10%	4.60%	4.20%	4.60%
Overall income tax rate	(15.70%)	(19.40%)	(9.80%)	(14.40%)
WPL [Member]
Effective Tax Rate [Line Items]
Statutory federal income tax rate	35.00%	35.00%	35.00%	35.00%
Effect of rate-making on property-related differences	(0.70%)	(0.20%)	(0.60%)	(0.70%)
Production tax credits	(6.70%)	(5.80%)	(6.40%)	(6.20%)
Other items, net	4.60%	5.00%	4.70%	4.90%
Overall income tax rate	32.20%	34.00%	32.70%	33.00%

X

- Definition

Effective Income Tax Rate Reconciliation Effect Of Rate Making On Property Related Differences

+ References

No definition available.

+ Details

Name:	lnt_EffectiveIncomeTaxRateReconciliationEffectOfRateMakingOnPropertyRelatedDifferences
Namespace Prefix:	lnt_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Effective income tax rate reconciliation tax benefit rider

+ References

No definition available.

+ Details

Name:	lnt_EffectiveIncomeTaxRateReconciliationTaxBenefitRider
Namespace Prefix:	lnt_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Effective tax rate

+ References

No definition available.

+ Details

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

X

- Definition

Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to 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 13



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



Reference 2: 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=26873400&loc=d3e23780-122690



Reference 3: 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 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

+ Details

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

X

- Definition

Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

+ 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 S99



-Paragraph 1



-Subparagraph (SAB TOPIC 6.I)



-URI http://asc.fasb.org/extlink&oid=34349781&loc=d3e330036-122817



Reference 3: 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

+ Details

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

X

- Definition

Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to deduction for qualified production activity.

+ References

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



-Publisher FASB



-Name Accounting Standards Codification



-Topic 740



-SubTopic 10



-Section S99



-Paragraph 1



-Subparagraph (SAB TOPIC 6.I)



-URI http://asc.fasb.org/extlink&oid=34349781&loc=d3e330036-122817



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 740



-SubTopic 10



-Section 50



-Paragraph 12



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

+ Details

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

X

- Definition

Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to other adjustments.

+ 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 S99



-Paragraph 1



-Subparagraph (SAB TOPIC 6.I)



-URI http://asc.fasb.org/extlink&oid=34349781&loc=d3e330036-122817



Reference 3: 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

+ Details

Name:	us-gaap_EffectiveIncomeTaxRateReconciliationOtherAdjustments
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
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: