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Stock-Based Compensation - Narrative (Details) - Outstanding options to purchase common stock - USD ($)
shares in Millions, $ in Millions
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award      
Intrinsic value $ 5.6 $ 5.4 $ 11.4
Unvested options outstanding (shares) 3.1    
Period for recognition 2 years 6 months    
Unrecognized compensation expense $ 23.2    
Maximum      
Share-based Compensation Arrangement by Share-based Payment Award      
Contractual term 10 years