Property, Plant and Equipment, and right-of-use assets - Schedule of Property, Plant and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 1,022,354
Less: accumulated depreciation	488,300
Net property, plant and equipment	534,054
Total property, plant and equipment		$ 919,078
Less: accumulated depreciation		435,544
Net property, plant and equipment		483,534
Land
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	33,654
Total property, plant and equipment		26,108
Land rights and buildings
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	94,157
Total property, plant and equipment		92,495
Plant and machinery
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	725,203
Total property, plant and equipment		673,919
Other equipment, furniture and fixtures
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	30,965
Total property, plant and equipment		28,460
Prepayments and construction in progress
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 138,374
Total property, plant and equipment		$ 98,096