ACQUISITION OF FOX ENERGY CENTER (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		1 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2013 Fox Energy Company LLC MW	Mar. 31, 2014 Fox Energy Company LLC
Acquisition
Purchase price	$ 0	$ 391.6	$ 391.6
Capacity of electric generating facility			593
Assets acquired
Inventories - materials and supplies			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