DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES - Gains or Losses Related to Changes in Fair Value and Cash Settlements on Derivatives Not Qualifying as Hedging Instruments (Details) - Not Designated as Hedging Instrument - Commodity contracts - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Derivatives, Fair Value [Line Items]
Cash settlements	$ 0	$ 17,385	$ 1,484
Change in fair value	0	(12,146)	12,146
Total gain on non-qualifying derivatives	$ 0	$ 5,239	$ 13,630