Financial instruments and derivatives - Location and Fair Values of Derivative Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Derivatives designated as hedging instruments | Commodity contracts | Prepaid expenses
Derivatives, Fair Value [Line Items]
Derivatives as hedging instruments, assets	$ 0	$ 282
Derivatives designated as hedging instruments | Commodity contracts | Other assets
Derivatives, Fair Value [Line Items]
Derivatives as hedging instruments, assets	0	0
Derivatives designated as hedging instruments | Commodity contracts | Accrued expenses and other
Derivatives, Fair Value [Line Items]
Derivatives hedging instrument, liabilities	(1,625)	(1,843)
Derivatives designated as hedging instruments | Commodity contracts | Other liabilities
Derivatives, Fair Value [Line Items]
Derivatives hedging instrument, liabilities	0	(10)
Derivatives designated as hedging instruments | Foreign exchange contracts | Prepaid expenses
Derivatives, Fair Value [Line Items]
Derivatives as hedging instruments, assets	1,236	770
Derivatives designated as hedging instruments | Foreign exchange contracts | Accrued expenses and other
Derivatives, Fair Value [Line Items]
Derivatives hedging instrument, liabilities	(178)	(2,482)
Derivatives not designated as hedging instruments | Foreign exchange contracts | Prepaid expenses
Derivatives, Fair Value [Line Items]
Derivatives as hedging instruments, assets	88	727
Derivatives not designated as hedging instruments | Foreign exchange contracts | Accrued expenses and other
Derivatives, Fair Value [Line Items]
Derivatives hedging instrument, liabilities	$ (34)	$ (561)