Goodwill and intangible assets - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Goodwill and intangible assets
Goodwill impairment loss	$ 0	$ 0
Goodwill	47,803	47,803
Amortization of Intangible Assets	2,862	$ 2,932
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months	2,800
Finite-Lived Intangible Assets, Amortization Expense, Year Two	2,800
Finite-Lived Intangible Assets, Amortization Expense, Year Three	2,800
Finite-Lived Intangible Assets, Amortization Expense, Year Four	2,800
Finite-Lived Intangible Assets, Amortization Expense, Year Five	2,500
Finite-Lived Intangible Assets, Amortization Expense, after Year Five	$ 9,500