SHORT-TERM DEBT AND LINES OF CREDIT (Details 2) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011 INTEGRYS ENERGY GROUP, INC.	Dec. 31, 2011 INTEGRYS ENERGY GROUP, INC. Maximum	Dec. 31, 2011 Commercial paper	Dec. 31, 2009 Commercial paper	Dec. 31, 2010 Short-term notes payable	Dec. 31, 2009 Short-term notes payable	Dec. 31, 2011 Revolving credit facility maturing on April 23, 2013 INTEGRYS ENERGY GROUP, INC.	Dec. 31, 2010 Revolving credit facility maturing on April 23, 2013 INTEGRYS ENERGY GROUP, INC.	Dec. 31, 2011 Revolving credit facility maturing on April 23, 2013 WPS	Dec. 31, 2010 Revolving credit facility maturing on April 23, 2013 WPS	Dec. 31, 2011 Revolving credit facility maturing on April 23, 2013 PGL	Dec. 31, 2010 Revolving credit facility maturing on April 23, 2013 PGL	Dec. 31, 2010 Revolving credit facility maturing on June 09, 2011 INTEGRYS ENERGY GROUP, INC.	Dec. 31, 2011 Revolving credit facility maturing on May 17, 2016 INTEGRYS ENERGY GROUP, INC.	Dec. 31, 2011 Revolving credit facility maturing on May 17, 2014 INTEGRYS ENERGY GROUP, INC.	Dec. 31, 2010 Revolving credit facility maturing on June 13, 2011 PELLC	Dec. 31, 2011 Revolving credit facility maturing on May 15, 2012 WPS	Dec. 31, 2010 Revolving short-term notes payable maturing on May 13, 2011 WPS
Short-term borrowings
Total short-term credit capacity	$ 1,710.0	$ 2,010.0							$ 735.0	$ 735.0	$ 115.0	$ 115.0	$ 250.0	$ 250.0	$ 500.0	$ 200.0	$ 275.0	$ 400.0	$ 135.0	$ 10.0
Letters of credit issued inside credit facilities	33.7	64.9
Short-term borrowings outstanding	303.3	10.0	92.6		303.3	212.1	10.0	10.0
Available capacity under existing agreements	$ 1,373.0	$ 1,935.1
Maximum debt to total capitalization ratio (as a percent)				65.00%