DERIVATIVE INSTRUMENTS - DERIVATIVES IN CASH FLOW HEDGING RELATIONSHIPS (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Losses reclassified from accumulated OCI into income	[1]	$ (46)	$ (46)	$ (46)
Realized gains losses, derivative instruments on energy-related contracts		$ (9,100)	$ 1,700	$ (400)

[1] Included in Interest Charges