Summary of Significant Accounting Policies - Concentration of Credit Risk (Details) - Customer	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2020 customer	Jun. 30, 2019 USD ($)	Jun. 30, 2020 customer	Jun. 30, 2019 USD ($)	Dec. 31, 2019 customer
Total revenue
Concentration risk
Number of major customers	3	1	3	1
Total revenue | Customer one
Concentration risk
Concentration risk	48.00%	40.00%	41.00%	24.00%
Total revenue | Customer two
Concentration risk
Concentration risk	16.00%		19.00%
Total revenue | Customer three
Concentration risk
Concentration risk	14.00%		14.00%
Accounts receivable
Concentration risk
Number of major customers			3		3
Accounts receivable | Customer one
Concentration risk
Concentration risk	48.00%		48.00%		39.00%
Accounts receivable | Customer two
Concentration risk
Concentration risk	21.00%		21.00%		18.00%
Accounts receivable | Customer three
Concentration risk
Concentration risk	16.00%		16.00%		11.00%