CASH AND CASH EQUIVALENTS - DISCONTINUED OPERATIONS (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating activities
Depreciation and amortization expense	$ 287.5	$ 263.4	$ 247.3
Net unrealized gains on energy contracts	(21.4)	(100.5)	(34.6)
Deferred income taxes and investment tax credits	165.9	209.8	146.0
Loss on sale of IES's retail energy business	24.3	0	0
Other	43.5	34.9	25.3
Investing activities
Capital expenditures	(865.0)	(669.2)	(594.4)
Discontinued operations
Operating activities
Depreciation and amortization expense	2.7	3.3	5.3
Net unrealized gains on energy contracts	(22.7)	(100.3)	(34.5)
Deferred income taxes and investment tax credits	36.1	56.1	(0.4)
Remeasurement of uncertain tax positions included in our liability for unrecognized tax benefits	(0.7)	(5.9)	(1.8)
Other	33.4	23.8	21.7
Investing activities
Capital expenditures	(0.8)	(2.6)	(2.0)
Discontinued operations \| Compass Energy Services, Inc.
Investing activities
Contingent consideration and payables related to the acquisition of Compass Energy Services	0	7.8	0
Discontinued operations \| IES's retail energy business
Operating activities
Loss on sale of IES's retail energy business	24.3	0	0
Discontinued operations \| WPS Westwood Generation, LLC
Investing activities
Portion of Westwood sale financed with note receivable	$ 0	$ 0	$ 4.0

Remeasurement of uncertain tax positions included in our liability for unrecognized tax benefits.

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Amount of deferred income tax expense (benefit) and income tax credits.

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The aggregate expense recognized in the current period that allocates the cost of tangible assets, intangible assets, or depleting assets to periods that benefit from use of the assets.

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Amount of gain (loss), before tax expense or benefit and not previously recognized, resulting from the sale of a business component.

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Amount of noncash consideration received for selling an asset or business through a noncash (or part noncash) transaction.

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Other cash or noncash adjustments to reconcile net income to cash provided by (used in) operating activities that are not separately disclosed in the statement of cash flows (for example, cash received or cash paid during the current period for miscellaneous operating activities, net change during the reporting period in other assets or other liabilities).

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The value of the noncash (or part noncash) consideration given (for example, liability, equity) in a transaction. Noncash is defined as transactions during a period that do not result in cash receipts or cash payments in the period. "Part noncash" refers to that portion of a transaction not resulting in cash receipts or cash payments in the period.

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The cash outflow associated with the acquisition of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale; includes cash outflows to pay for construction of self-constructed assets.

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The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of open agreements to purchase or sell energy at some future point, held at each balance sheet date, that was included in earnings for the period.

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