Asset Retirement Obligations (Asset Retirement Obligations Expected To Be Recognized) (Details) (Scenario, Forecast [Member], USD $) In Millions, unless otherwise specified	3 Months Ended
	Jun. 30, 2015
Asset Retirement Obligations [Line Items]
Expected ARO increase not to exceed	$ 85
IPL [Member]
Asset Retirement Obligations [Line Items]
Expected ARO increase not to exceed	75
WPL [Member]
Asset Retirement Obligations [Line Items]
Expected ARO increase not to exceed	$ 10