DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES - Commodity Derivative Instruments (Details) gal in Thousands	9 Months Ended
	Sep. 30, 2017 gal
Derivatives NOT Designated as Hedging Instruments | Physical fixed-price derivative contracts | Current
Derivative Instruments And Hedging Activities
Volume (in gallons)	7,115
Derivatives NOT Designated as Hedging Instruments | Physical fixed-price derivative contracts | Long-Term
Derivative Instruments And Hedging Activities
Volume (in gallons)	1,110
Derivatives NOT Designated as Hedging Instruments | Physical index derivative contracts | Current
Derivative Instruments And Hedging Activities
Volume (in gallons)	35,385
Derivatives NOT Designated as Hedging Instruments | Physical index derivative contracts | Long-Term
Derivative Instruments And Hedging Activities
Volume (in gallons)	0
Derivatives NOT Designated as Hedging Instruments | Futures contracts for refined petroleum products | Current
Derivative Instruments And Hedging Activities
Volume (in gallons)	241
Derivatives NOT Designated as Hedging Instruments | Futures contracts for refined petroleum products | Long-Term
Derivative Instruments And Hedging Activities
Volume (in gallons)	6,090
Derivatives Designated as Hedging Instruments | Cash Flow Hedge | Physical fixed-price derivative contracts | Current
Derivative Instruments And Hedging Activities
Volume (in gallons)	1,050
Derivatives Designated as Hedging Instruments | Cash Flow Hedge | Physical fixed-price derivative contracts | Long-Term
Derivative Instruments And Hedging Activities
Volume (in gallons)	0
Derivatives Designated as Hedging Instruments | Cash Flow Hedge | Cash flow hedge futures contracts | Current
Derivative Instruments And Hedging Activities
Volume (in gallons)	13,104
Derivatives Designated as Hedging Instruments | Cash Flow Hedge | Cash flow hedge futures contracts | Long-Term
Derivative Instruments And Hedging Activities
Volume (in gallons)	8,400
Derivatives Designated as Hedging Instruments | Fair Value Hedge | Futures contracts for refined petroleum products | Current
Derivative Instruments And Hedging Activities
Volume (in gallons)	100,632
Derivatives Designated as Hedging Instruments | Fair Value Hedge | Futures contracts for refined petroleum products | Long-Term
Derivative Instruments And Hedging Activities
Volume (in gallons)	4,494