Balance sheet components - Property, Plant and Equipment, net (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 241,211,000	$ 246,483,000
Less: Accumulated depreciation	(160,078,000)	(146,393,000)
Property, plant and equipment, net	81,133,000	100,090,000
Depreciation expense	27,700,000	29,900,000	$ 27,000,000.0
Asset impairment charges	0	1,000,000.0	400,000
Purchases of property, plant and equipment, unpaid	1,900,000	1,500,000	10,000,000.0
Land
Property, Plant and Equipment [Line Items]
Property, plant and equipment	3,197,000	3,157,000
Buildings
Property, Plant and Equipment [Line Items]
Property, plant and equipment	23,624,000	23,379,000
Asset impairment charges			$ 100,000
Machinery and equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment	181,596,000	187,746,000
Furniture, fixtures, software and office equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment	10,736,000	10,201,000
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 22,058,000	$ 22,000,000