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Stock Plans - RSAs, RSUs, PSAs and PSUs FV Assumptions (Details) - $ / shares
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
RSAs, RSUs, PSAs and PSUs      
Assumptions      
Weighted average fair value (in dollars per share) $ 11.53 $ 17.37 $ 29.22
Performance share units      
Assumptions      
Weighted average fair value (in dollars per share) $ 16.45 $ 15.58  
Dividend yield (as a percent) 0.00% 0.00%  
Expected volatility factor (as a percent) 53.00% 49.00%  
Risk-free interest rate (as a percent) 2.37% 2.88%  
Expected life (in years) 2 years 9 months 18 days 3 years