Property, Plant and Equipment (Electric Plant) (Details) (USD $) In Millions, unless otherwise specified																										12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013 Generation [Member]	Dec. 31, 2012 Generation [Member]	Dec. 31, 2013 Distribution [Member]	Dec. 31, 2012 Distribution [Member]	Dec. 31, 2013 Other [Member]	Dec. 31, 2012 Other [Member]	Dec. 31, 2013 IPL [Member]	Dec. 31, 2012 IPL [Member]	Dec. 31, 2013 IPL [Member] Generation [Member]	Dec. 31, 2012 IPL [Member] Generation [Member]	Dec. 31, 2013 IPL [Member] Distribution [Member]	Dec. 31, 2012 IPL [Member] Distribution [Member]	Dec. 31, 2013 IPL [Member] Other [Member]	Dec. 31, 2012 IPL [Member] Other [Member]	Dec. 31, 2013 IPL [Member] George Neal Unit 4 [Member]	Dec. 31, 2013 WPL [Member]	Dec. 31, 2012 WPL [Member]	Dec. 31, 2013 WPL [Member] Generation [Member]	Dec. 31, 2012 WPL [Member] Generation [Member]	Dec. 31, 2013 WPL [Member] Distribution [Member]	Dec. 31, 2012 WPL [Member] Distribution [Member]	Dec. 31, 2013 WPL [Member] Other [Member]	Dec. 31, 2012 WPL [Member] Other [Member]	Dec. 31, 2013 WPL [Member] Edgewater Unit 3 and Nelson Dewey Units 1 and 2 [Member]
Property, Plant and Equipment [Line Items]
Plant in service			$ 4,792.0	$ 4,798.9	$ 4,179.6	$ 3,981.5	$ 286.3	$ 290.3			$ 2,513.2	$ 2,393.0	$ 2,311.2	$ 2,205.9	$ 210.5	$ 216.3				$ 2,278.8	$ 2,405.9	$ 1,868.4	$ 1,775.6	$ 75.8	$ 74.0
Plant anticipated to be retired early	157.8	0							0	0								157.8	0
Electric plant	$ 9,415.7	$ 9,070.7							$ 5,034.9	$ 4,815.2							$ 61.0	$ 4,380.8	$ 4,255.5
Property, plant and equipment, useful life																										10 years