Income taxes - Narrative (Details) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) $ / shares subsidiary	Dec. 31, 2018 USD ($) $ / shares	Dec. 31, 2017 USD ($)
Operating Loss Carryforwards [Line Items]
Provisional income tax expense (benefit)			$ 69,900
Provisional income tax expense (benefit), adjustment		$ 4,200
Provisional income tax expense (benefit), tax for accumulated foreign earnings	$ 2,600
Provisional tax on foreign earnings	679,000
Foreign income tax benefit	(10,156)	(14,273)	$ (9,352)
Unremitted earnings from foreign subsidiaries	5,300
Significant change in unrecognized tax benefits is reasonably possible, amount of unrecorded benefit	2,800
Interest and penalties related to income tax matters	400	600
Federal
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards, valuation allowance	$ 600
Foreign
Operating Loss Carryforwards [Line Items]
Number of subsidiaries | subsidiary	14
Net operating loss carryforward	$ 981,000
Malaysia
Operating Loss Carryforwards [Line Items]
Foreign income tax benefit	$ 3,400	$ 4,000
Income tax benefit of tax holiday on per share basis (in dollars per share) | $ / shares	$ 0.03	$ 0.03
Expiring 2021 To 2034 | Federal
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	$ 700
Expiring 2020 To 2038 | Foreign
Operating Loss Carryforwards [Line Items]
Net operating loss carryforward	973,000
Carried Forward Indefinitely | Foreign
Operating Loss Carryforwards [Line Items]
Net operating loss carryforward	$ 8,000