COMMON STOCK (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	30,212,453	29,872,825	29,796,232
New issues during period [Abstract]
Dividend Reinvestment Plan	1,397,583	259,359	0
Stock-Based Compensation Plan	43,226	80,269	76,593
Ending balance	31,653,262	30,212,453	29,872,825
Par value of common stock (in dollars per share)	$ 1.25	$ 1.25
Net excess over par value recorded in premium on common stock	$ 72.5	$ 16.0	$ 2.8
Incremental shares included in diluted earnings per share	79,475	86,031	112,551
Equity capital raised through Dividend Reinvestment Plan	$ 70.2	$ 13.4