Summary Of Significant Accounting Policies (Schedule Of Allowance For Funds Used During Construction Recovery Rate) (Details)	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
IPL [Member] | IPL (FERC formula - Marshalltown CWIP) [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Recovery rates	8.00%	[1]	0.00%	[1]	0.00%	[1]
IPL [Member] | IPL (FERC formula - other CWIP) [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Recovery rates	7.80%		8.20%		8.20%
IPL [Member] | Marshalltown Generating Station [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Return on common equity for calculation of AFUDC	10.30%
WPL [Member] | WPL (PSCW formula - retail jurisdiction) [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Recovery rates	8.20%		8.20%		8.80%
WPL [Member] | WPL (FERC formula - wholesale jurisdiction) [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Recovery rates	4.10%		4.50%		7.90%

[1] In 2013, the IUB issued an order establishing rate-making principles for Marshalltown that requires a 10.3% return on common equity for the calculation of AFUDC related to the construction of such facility.