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Stockholders' Equity and Stock-based Compensation (Restricted Stock Units and Restricted Stock Awards Activity) (Details) - Restricted Stock Units - $ / shares
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Number of Shares      
Beginning balance (in shares) 1,226,883 1,410,588 587,333
Granted (in shares) 595,985 548,245 1,326,849
Vested (in shares) (438,892) (525,375) (368,367)
Canceled (in shares) (169,158) (206,575) (135,227)
Ending balance (in shares) 1,214,818 1,226,883 1,410,588
Expected to vest as of December 31, 2016 902,794    
Weighted-Average Grant Date Fair Value Per Share      
Beginning balance (usd per share) $ 55.71 $ 40.34 $ 28.85
Granted (in shares) 81.59 75.44 42.69
Vested (in shares) 53.17 39.87 33.52
Canceled (in shares) 65.51 43.43 32.04
Ending balance (usd per share) 67.99 $ 55.71 $ 40.34
Expected to vest as of December 31, 2016 $ 66.37