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DERIVATIVE FINANCIAL INSTRUMENTS - Commodity Price Risk Management (Details)
$ in Thousands, gal in Millions
 12 Months Ended
Dec. 31, 2017
USD ($)
gal
Dec. 31, 2016
USD ($)
gal
Disclosure of detailed information about financial instruments [line items]    
Premiums realized on written foreign exchange call options $ (2,925) $ (2,569)
Realized loss on warrants   543
Unrealized loss (gain) on warrants 15 (580)
Realized (gain) loss on currency and commodity derivatives (10,832) 357
Unrealized gain on currency and commodity derivatives (7,248) (7,219)
Gain on derivative financial instruments $ (20,990) $ (9,468)
Heating Oil Commodity Derivative    
Disclosure of detailed information about financial instruments [line items]    
Derivative financial instruments outstanding (in volume) | gal 5.0 1.0
Metal Commodity Derivative    
Disclosure of detailed information about financial instruments [line items]    
Notional amount $ 0 $ 0