Income Taxes (Narrative) (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2014
Income Taxes [Line Items]
Increase (decrease) non-current deferred tax liabilities	$ 77.2
IPL [Member]
Income Taxes [Line Items]
Increase (decrease) non-current deferred tax liabilities	57.0
WPL [Member]
Income Taxes [Line Items]
Increase (decrease) non-current deferred tax liabilities	$ 21.1