Common Equity (Capital Transactions With Subsidiaries) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Common stock dividends	$ 247.3	$ 225.8	$ 208.3
IPL [Member]
Common stock dividends	140.0	140.0	128.1
Repayments of capital	0.0	0.0	0.0
Total distributions from common equity	140.0	140.0	128.1
WPL [Member]
Common stock dividends	126.9	118.7	116.3
Repayments of capital	0.0	0.0	0.0
Total distributions from common equity	126.9	118.7	116.3
Resources [Member]
Common stock dividends	0.0	0.0	0.0
Repayments of capital	0.0	50.0	95.0
Total distributions from common equity	$ 0.0	$ 50.0	$ 95.0