REGULATORY ASSETS AND LIABILITIES (Details 2) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Regulatory Liabilities
Current liabilities	$ 38.0	$ 27.6
Long-term liabilities	286.3	281.0
Total regulatory liabilities	324.3	308.6
Removal costs
Regulatory Liabilities
Total regulatory liabilities	238.0	233.3
Decoupling
Regulatory Liabilities
Total regulatory liabilities	24.3	15.7
Energy costs refundable through rate adjustments
Regulatory Liabilities
Total regulatory liabilities	21.9	22.7
Unrecognized pension and other postretirement benefit costs
Regulatory Liabilities
Total regulatory liabilities	18.5	17.7
Crane Creek depreciation deferral
Regulatory Liabilities
Total regulatory liabilities	9.0	9.4
Fox Energy Center
Regulatory Liabilities
Total regulatory liabilities	5.6	0
Other Disclosures
Amount of allowance for earnings on equity capitalized for rate making purposes not included in the deferral	26.7
Other
Regulatory Liabilities
Total regulatory liabilities	$ 7.0	$ 9.8