Derivatives (Details 2) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Commodity | Cost of Sales and Merchandising Revenues
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives instruments	$ (25,236)	$ 27,025
Not Designated as Hedging Instrument | Interest rate contracts | Interest Income (Expense)
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives instruments	1,408	389
Not Designated as Hedging Instrument | Foreign currency contract | Other Income
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives instruments	$ (1,122)	$ 98