DISPOSITIONS - DISCONTINUED OPERATIONS (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		6 Months Ended
	Nov. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Components of discontinued operations recorded on income statements
Discontinued operations, net of tax		$ 0.0	$ (0.8)	$ (0.8)	$ 12.1
Corporate and Other | IES's retail energy business
Disclosures related to discontinued operations
Proceeds from sale	$ 331.8
Transition period for services	15 months
Components of discontinued operations recorded on income statements
Revenues			596.3	0.0	1,885.9
Cost of sales			(556.7)	0.0	(1,791.5)
Operating and maintenance expense			(27.7)	(1.2)	(60.5)
Depreciation and amortization expense			(0.8)	0.0	(1.5)
Property and revenue taxes			(0.7)	(0.2)	(1.1)
Goodwill impairment loss			(6.7)	0.0	(6.7)
Transaction costs			(0.8)	0.0	(0.8)
Miscellaneous income			0.3	0.1	0.5
Interest expense			(0.2)	0.0	(0.4)
Income (loss) before taxes			3.0	(1.3)	23.9
(Provision) benefit for income taxes			(3.7)	0.5	(11.6)
Discontinued operations, net of tax		$ 0.0	$ (0.7)	$ (0.8)	$ 12.3