Basis of presentation and significant accounting policies (Details) - USD ($)	3 Months Ended		6 Months Ended			12 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020	Dec. 31, 2020
Concentration Risk [Line Items]
Asset impairment charges				$ 0
Customer one | Customer concentration | Revenue
Concentration Risk [Line Items]
Percentage of concentration of credit risk	10.00%	10.00%	10.00%		10.00%
Customer two | Customer concentration | Revenue
Concentration Risk [Line Items]
Percentage of concentration of credit risk	10.00%		10.00%
Customer three | Customer concentration | Revenue
Concentration Risk [Line Items]
Percentage of concentration of credit risk	10.00%		10.00%
Customer four | Customer concentration | Revenue
Concentration Risk [Line Items]
Percentage of concentration of credit risk			10.00%
Top five customers | Customer concentration | Revenue
Concentration Risk [Line Items]
Percentage of concentration of credit risk	77.00%	82.00%	76.00%		83.00%
Huawei | Customer concentration | Revenue
Concentration Risk [Line Items]
Percentage of concentration of credit risk		52.00%			52.00%
Three customers | Customer concentration | Accounts Receivable
Concentration Risk [Line Items]
Percentage of concentration of credit risk			57.00%			65.00%