COMMON EQUITY - CHANGES TO ISSUED COMMON STOCK (Details)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2011
Roll forward of issued common stock
Common stock issued, balance at beginning of the period	79,919,176	78,287,906	78,287,906
Shares issued - Stock-based compensation		972,718
Shares issued - Stock Investment Plan	12,151	298,532
Shares issued - Employee Stock Ownership Plan	31,764	248,724
Shares issued - Rabbi trust shares		111,296
Common stock issued, balance at end of the period	79,963,091	79,919,176	78,287,906