DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES - Commodity Derivative Instruments Outstanding (Details) gal in Thousands	12 Months Ended
	Dec. 31, 2018 gal
Derivatives NOT Designated as Hedging Instruments | Current Derivative Contract | Physical fixed price derivative contracts
Derivative Instruments And Hedging Activities
Volume (in gallons)	23,119
Derivatives NOT Designated as Hedging Instruments | Current Derivative Contract | Physical index derivative contracts
Derivative Instruments And Hedging Activities
Volume (in gallons)	52,912
Derivatives NOT Designated as Hedging Instruments | Current Derivative Contract | Futures contracts for refined petroleum products
Derivative Instruments And Hedging Activities
Volume (in gallons)	29,771
Derivatives NOT Designated as Hedging Instruments | Long-term Derivative Contract | Physical fixed price derivative contracts
Derivative Instruments And Hedging Activities
Volume (in gallons)	4,765
Derivatives NOT Designated as Hedging Instruments | Long-term Derivative Contract | Physical index derivative contracts
Derivative Instruments And Hedging Activities
Volume (in gallons)	0
Derivatives NOT Designated as Hedging Instruments | Long-term Derivative Contract | Futures contracts for refined petroleum products
Derivative Instruments And Hedging Activities
Volume (in gallons)	9,996
Derivatives Designated as Hedging Instruments | Current Derivative Contract | Futures contracts for refined petroleum products | Fair Value Hedge
Derivative Instruments And Hedging Activities
Volume (in gallons)	107,184
Derivatives Designated as Hedging Instruments | Long-term Derivative Contract | Futures contracts for refined petroleum products | Fair Value Hedge
Derivative Instruments And Hedging Activities
Volume (in gallons)	420