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Stock-Based Compensation - Aggregate Intrinsic Value of Options (Details) - Stock Options - USD ($)
$ / shares in Units, $ in Thousands
3 Months Ended
Mar. 31, 2020
Mar. 31, 2019
Stock-based compensation    
Aggregate intrinsic value of options exercised $ 194 $ 16,059
Cash received from the exercise of stock options $ 71 $ 2,923
Weighted average grant date fair value per option $ 28.51 $ 42.35