COMMON EQUITY - RECONCILIATION OF SHARES ISSUED AND OUTSTANDING (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Reconciliation of Shares Outstanding [Abstract]
Common stock issued (in shares)	79,963,091	79,919,176	78,287,906	78,287,906
Deferred compensation rabbi trust (in shares)	428,920	473,796
Average cost of shares in the rabbi trust (in dollars per share)	$ 48.73	$ 48.50
Total common shares outstanding	79,534,171	79,445,380