Accounts and notes payable (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Accounts and notes payable
Accounts payable - unrelated parties	$ 121,250	$ 110,246
Notes payable - unrelated parties	68,665	69,929
Accounts and notes payable - unrelated parties	189,915	180,175
Accounts and notes payable - related parties	11,518	6,492
Total	201,433	186,667
Cash pledged as collateral	31,700	29,700
Notes receivable pledged as collateral	1,900	7,400
Land use right pledged as collateral	$ 40,100	$ 37,800