ASSET RETIREMENT OBLIGATIONS (Details) (USD $)	12 Months Ended						3 Months Ended	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011 Utilities	Dec. 31, 2010 Utilities	Dec. 31, 2009 Utilities	Dec. 31, 2009 Utilities WPS MW	Dec. 31, 2011 Integrys Energy Services	Dec. 31, 2010 Integrys Energy Services	Dec. 31, 2009 Integrys Energy Services
Changes in asset retirement obligations
Asset retirement obligations at the beginning of the period	$ 320,900,000	$ 195,100,000	$ 179,100,000	$ 320,900,000	$ 194,800,000	$ 178,900,000			$ 300,000	$ 200,000
Accretion	17,100,000	11,700,000	9,700,000	17,100,000	11,700,000	9,600,000				100,000
Asset retirement obligations transferred in sale		(300,000)							(300,000)
Additions and revisions to estimated cash flows	64,900,000	120,500,000	6,300,000	64,400,000	120,500,000	6,300,000	6,300,000	500,000
Settlements	(5,700,000)	(6,100,000)		(5,700,000)	(6,100,000)
Asset retirement obligations at the end of the period	$ 397,200,000	$ 320,900,000	$ 195,100,000	$ 396,700,000	$ 320,900,000	$ 194,800,000		$ 500,000		$ 300,000
Crane Creek wind generation project capacity (in megawatts)							99