Benefit Plans (Narrative) (Details) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2015 USD ($)	Sep. 30, 2015 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Percentage of employees accepting voluntary separation package	2.00%
Voluntary employee separation charges	$ 8.0
Unrecognized compensation cost	6.0	$ 6.0
Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Unrecognized compensation cost recognized over a weighted average period		1 year
Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Unrecognized compensation cost recognized over a weighted average period		2 years
IPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Voluntary employee separation charges	5.0
WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Voluntary employee separation charges	$ 3.0