Concentration of Risk (Details) - customer	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Revenue | Customer concentration risk
Concentration of Risk
Number of customers	2	3	1	3
Revenue | Customer concentration risk | First customer
Concentration of Risk
Percentage of concentration risk	19.70%	22.50%	24.40%	19.70%
Revenue | Customer concentration risk | Second customer
Concentration of Risk
Percentage of concentration risk	10.20%	22.20%	29.60%	18.50%
Revenue | Customer concentration risk | Third customer
Concentration of Risk
Percentage of concentration risk		11.60%	29.60%	16.20%
Consolidated accounts receivable | Credit concentration risk
Concentration of Risk
Number of customers			2		2
Consolidated accounts receivable | Credit concentration risk | First customer
Concentration of Risk
Percentage of concentration risk			11.70%		23.80%
Consolidated accounts receivable | Credit concentration risk | Second customer
Concentration of Risk
Percentage of concentration risk			10.00%		11.90%