v2.4.0.6

Summary Of Significant Accounting Policies (Schedule Of Average Rates Of Depreciation) (Details)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Electric - generation [Member] | IPL [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Average rate of depreciation	3.70%	3.50%	3.70%
Electric - generation [Member] | WPL [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Average rate of depreciation	3.20%	3.30%	2.90%
Electric - distribution [Member] | IPL [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Average rate of depreciation	2.50%	2.40%	2.70%
Electric - distribution [Member] | WPL [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Average rate of depreciation	2.90%	2.90%	2.60%
Gas [Member] | IPL [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Average rate of depreciation	3.40%	3.50%	3.30%
Gas [Member] | WPL [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Average rate of depreciation	2.60%	2.60%	2.20%
Other [Member] | IPL [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Average rate of depreciation	4.50%	4.80%	4.90%
Other [Member] | WPL [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Average rate of depreciation	5.30%	5.20%	6.50%

X

- Definition

Composite depreciation rate for public utility plants in service.

+ References

No definition available.

+ Details

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

X

- Details

Name:	us-gaap_PublicUtilityPropertyPlantAndEquipmentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration