ACQUISITIONS (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended			1 Months Ended	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014 Alliant Energy Corporation's natural gas distribution business in southeast Minnesota MERC	Mar. 31, 2013 Fox Energy Company LLC WPS MW	Sep. 30, 2014 Fox Energy Company LLC WPS
Acquisitions
Estimated purchase price			$ 14
Purchase price	0	391.6		391.6
Capacity of electric generating facility				593
Assets acquired
Inventories				3.0
Other current assets				0.4
Property, plant, and equipment				374.4
Other long-term assets				15.6
Total assets acquired				393.4
Liabilities assumed
Accounts payable				1.8
Total liabilities assumed				1.8
Contracted capacity from power purchase agreement				500
Termination of tolling agreement with Fox Energy Company LLC	$ 0	$ (50.0)		$ 50.0
Amortization period of regulatory asset					9 years