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Share-Based Compensation - Stock Options Narrative (Details) - USD ($)
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Share-based compensation      
Stock options granted (in shares) 0 0 0
Unrecognized compensation costs related to stock options $ 0    
Stock Options      
Share-based compensation      
Recognized share-based compensation expense $ 0 $ 0 $ 0