Commitments and Contingencies - Concentrations of Credit Risk (Details) - Customers - customer	6 Months Ended	12 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Accounts receivable \| Credit risk
Customer Concentration
Concentration Risk Number of Customers	2		2
Concentration risk (as a percent)	88.40%		63.40%
Revenues \| Customer concentration
Customer Concentration
Concentration Risk Number of Customers	2	2
Concentration risk (as a percent)	77.90%	66.00%

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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