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Derivative Financial Instruments - Hedges (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) item	Dec. 31, 2018 USD ($) item	Dec. 31, 2017 USD ($) item
Fair Value Hedge \| Futures contracts \| Cost of sales
Fair values of derivative financial instruments
Amount of Gain (Loss) Recognized in Income on Derivatives	$ 10,640	$ 5,566	$ 26,118
Fair Value Hedge \| Inventories \| Cost of sales
Fair values of derivative financial instruments
Amount of Gain (Loss) Recognized in Income on Hedged Items	$ (10,532)	$ (9,686)	$ (23,247)
Cash Flow Hedges
Fair values of derivative financial instruments
Number of agreements in place \| item	0
Cash Flow Hedges \| Interest Rate Swaps
Fair values of derivative financial instruments
Number of agreements in place \| item		1	1
Hedged borrowings		$ 100,000	$ 100,000
Cash Flow Hedges \| Interest Rate Swaps \| London Interbank Offered Rate (LIBOR) [Member]
Fair values of derivative financial instruments
Fixed rate (as a percent)		1.819%	1.819%
Derivatives designated as hedging instruments \| Cash Flow Hedges
Fair values of derivative financial instruments
Amount of Gain (Loss) Recognized in Other Comprehensive Income on Derivatives, preadoption		$ 100	$ 1,000
Gain (Loss) on Interest Rate Cash Flow Hedge Ineffectiveness, preadoption		$ 0	$ 0