Income Taxes (Narrative) (Details) - Scenario, Forecast [Member] $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($)
Income Tax [Line Items]
Deductions in income tax return	$ 350
IPL [Member]
Income Tax [Line Items]
Deductions in income tax return	100
WPL [Member]
Income Tax [Line Items]
Deductions in income tax return	$ 200