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Summary of Significant Accounting Policies - Suppliers Accounted for 10% or More of Research and Development Expenses and Inventory Purchases (Parenthetical) (Details)
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Research and Development Expenses | Concentration of Suppliers      
Significant Accounting Policies [Line Items]      
Concentration risk percentage 10.00% 10.00% 10.00%