Income taxes - Schedule of Deferred Tax Assets and Liabilities Within the Same Jurisdiction (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Deferred tax assets	$ 15	$ 25	$ 56
Deferred tax liabilities	21,892	16,753	20,217
Net deferred tax liabilities	$ 21,877	$ 16,728	$ 20,161