DISPOSITIONS - DISCONTINUED OPERATIONS (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		1 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Nov. 30, 2014	Dec. 31, 2014	Nov. 01, 2014
Assets and liabilities included in disposal group on balance sheets
Total assets	$ 51.5			$ 52.2
Total liabilities	13.6			13.8
Components of discontinued operations recorded in income statements
Discontinued operations, net of tax	(0.9)	12.9
IES | IES's retail energy business
Assets and liabilities included in disposal group on balance sheets
Cash and cash equivalents					7.6
Accounts receivable and accrued unbilled revenues, net of reserves					293.4
Accounts receivable and accrued unbilled revenues, reserves					1.8
Inventories					52.2
Current assets from risk management activities					234.8
Other current assets					75.1
Property, plant, and equipment, net of accumulated depreciation					4.5
Accumulated depreciation					16.6
Long-term assets from risk management activities					106.9
Other long-term assets					25.5
Total assets					800.0
Accounts payable					186.9
Current liabilities from risk management activities					169.7
Accrued taxes					0.8
Other current liabilities					6.7
Long-term liabilities from risk management activities					79.5
Other long-term liabilities					0.3
Total liabilities					443.9
Components of discontinued operations recorded in income statements
Revenues	0	1,289.6
Cost of sales	0	(1,234.8)
Operating and maintenance expense	(1.2)	(32.0)
Depreciation and amortization expense	0	(0.7)
Taxes other than income taxes	(0.2)	(1.2)
Miscellaneous income	0.1	0.2
Interest expense	0	(0.2)
(Loss) income before taxes	(1.3)	20.9
Benefit (provision) for income taxes	0.5	(7.9)
Discontinued operations, net of tax	(0.8)	13.0
Disclosures related to discontinued operations
Proceeds from sale			331.8
Transition period for services			15 months
Holding Company and Other
Assets and liabilities included in disposal group on balance sheets
Property, plant, and equipment, net of accumulated depreciation	31.1			32.1
Total assets	50.8			51.5
Total liabilities	13.6			13.8
Holding Company and Other | Combined Locks Energy Center
Assets and liabilities included in disposal group on balance sheets
Total assets	0.7			0.7
Components of discontinued operations recorded in income statements
Discontinued operations, net of tax	$ 0.1