Property, plant and equipment - Major classes of property, plant and equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Property, plant and equipment
Property, plant and equipment, gross	$ 1,701,699	$ 1,585,782
Less: Accumulated depreciation	(439,767)	(417,738)
Total property, plant and equipment, net of accumulated depreciation	1,261,932	1,168,044
Land and buildings
Property, plant and equipment
Property, plant and equipment, gross	1,202,847	1,126,496
Machinery and equipment
Property, plant and equipment
Property, plant and equipment, gross	192,077	181,670
Furniture, fixtures and equipment
Property, plant and equipment
Property, plant and equipment, gross	301,751	263,716
River cruise ship and canal boats
Property, plant and equipment
Property, plant and equipment, gross	$ 5,024	$ 13,900