DISCONTINUED OPERATIONS (Details 2) (USD $) In Millions, unless otherwise specified	12 Months Ended							1 Months Ended	12 Months Ended			1 Months Ended	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013 Integrys Energy Services Combined Locks Energy Center	Dec. 31, 2012 Integrys Energy Services Combined Locks Energy Center	Dec. 31, 2011 Integrys Energy Services Combined Locks Energy Center	Dec. 31, 2011 Integrys Energy Services Energy Management Consulting Business	Mar. 31, 2013 Integrys Energy Services WPS Empire State, Inc WPS Beaver Falls Generation, LLC and WPS Syracuse Generation, LLC	Dec. 31, 2013 Integrys Energy Services WPS Empire State, Inc WPS Beaver Falls Generation, LLC and WPS Syracuse Generation, LLC	Dec. 31, 2012 Integrys Energy Services WPS Empire State, Inc WPS Beaver Falls Generation, LLC and WPS Syracuse Generation, LLC	Dec. 31, 2011 Integrys Energy Services WPS Empire State, Inc WPS Beaver Falls Generation, LLC and WPS Syracuse Generation, LLC	Nov. 30, 2012 Integrys Energy Services Sunbury Holdings, LLC WPS Westwood Generation, LLC	Dec. 31, 2012 Integrys Energy Services Sunbury Holdings, LLC WPS Westwood Generation, LLC	Dec. 31, 2011 Integrys Energy Services Sunbury Holdings, LLC WPS Westwood Generation, LLC	Sep. 30, 2012 Integrys Energy Services Sunbury Holdings, LLC WPS Westwood Generation, LLC
Discontinued operations
Cash proceeds related to sale								$ 1.6				$ 2.6
Earn-out mechanism period								4 years
Pre-tax impairment loss										1.1					8.4
After-tax impairment loss										0.7					5.0
Carrying value of the derivative contract liabilities assumed by the buyer								6.8
Period from the sale of discontinued operations within which cash flows will expire								2 years
Note receivable from the buyer												4.0
Term of note receivable from the buyer												7 years 6 months
Assets and liabilities classified as held for sale on balance sheets
Inventories				0.5	0.5			1.8		1.8		1.0
Current assets from risk management activities												0.1
Other current assets								0.2		0
Property, plant, and equipment, net of accumulated depreciation				0.2	2.0			5.7		5.7		5.5
Accumulated depreciation				0	0.5
Other long-term assets								0.1		0.1		1.1
Total assets				0.7	2.5			7.8		7.6		7.7
Other current liabilities								0.4		0.2
Long-term liabilities from risk management activities												0.1
Components of discontinued operations recorded in income statements
Nonregulated revenues				(0.1)	0.3	7.9			1.2	0.6	5.0		9.2	12.4
Nonregulated cost of sales				(0.2)	(0.5)	(2.0)			(0.9)	(2.0)	(2.3)		(4.4)	(5.6)
Operating and maintenance expense				(2.1)	(0.5)	(0.7)			0.4	(3.5)	(3.3)		(14.3)	(5.7)
Depreciation and amortization expense				0	(0.2)	(0.3)			0	(0.6)	(0.7)		(1.0)	(1.4)
Taxes other than income taxes				0	(0.1)	(0.2)			(0.3)	(1.4)	(0.9)		(0.2)	(0.2)
Miscellaneous income									0	0.3	0		0	0.1
Interest expense													(0.7)	(0.6)
Income (loss) before taxes				(2.4)	(1.0)	4.7			0.4	(6.6)	(2.2)		(11.4)	(1.0)
(Provision) benefit for income taxes	6.9	9.3	(1.1)	1.1	0.4	(1.8)			(0.2)	2.6	0.9		4.5	0.3
Discontinued operations, net of tax	4.8	(9.7)	0.5	(1.3)	(0.6)	2.9	0.1		0.2	(4.0)	(1.3)		(6.9)	(0.7)
Gain (loss) on sale at closing									$ 1.0				$ (0.6)