Income taxes - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Tax Credit Carryforward [Line Items]
Total income tax benefit resulting from the 2017 Act			$ 7,800
Transition tax expense (benefit) on deemed repatriation of deferred foreign income	$ 0	$ (624)	1,213
Federal and state income tax benefits related to the remeasurement of deferred tax assets and liabilities		800
Net deferred tax liabilities	24,312	9,639
Deferred tax assets relating to NOL carryforwards	7,017	6,936
U.S. Federal
Tax Credit Carryforward [Line Items]
Total income tax benefit resulting from the 2017 Act			7,200
State
Tax Credit Carryforward [Line Items]
Total income tax benefit resulting from the 2017 Act		100	$ 600
Foreign
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	$ 2,200
Retained Earnings
Tax Credit Carryforward [Line Items]
Reclassification of net tax expense from AOCI to retained earning		$ 1,000