Commitments And Contingencies (Schedule Of Environmental Liabilities) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Current environmental liabilities	$ 3.6	$ 3.7
Non-current environmental liabilities	15.4	25.3
Total environmental liabilities	19.0	29.0
IPL [Member]
Current environmental liabilities	2.8	2.5
Non-current environmental liabilities	13.6	23.2
Total environmental liabilities	16.4	25.7
WPL [Member]
Current environmental liabilities	0.8	1.2
Non-current environmental liabilities	1.7	2.1
Total environmental liabilities	$ 2.5	$ 3.3