Income Taxes (Narrative) (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2014
Income Taxes [Line Items]
Increase (decrease) non-current deferred tax liabilities	$ 177.6
IPL [Member]
Income Taxes [Line Items]
Increase (decrease) non-current deferred tax liabilities	123.6
WPL [Member]
Income Taxes [Line Items]
Increase (decrease) non-current deferred tax liabilities	$ 54.6