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Segment Reporting - Narrative (Details) - segment
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Revenue, Major Customer [Line Items]      
Number of operating segments 1 1 1
Concentration risk percentage     95.00%
Outside of the United States | Revenue | Geographic Concentration Risk      
Revenue, Major Customer [Line Items]      
Concentration risk percentage 2.00% 2.00% 2.00%