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Stock-Based Compensation - Restricted Stock and Restricted Stock Units Activity (Details) - Restricted stock
3 Months Ended
Mar. 31, 2018
$ / shares
shares
NUMBER OF SHARES  
Beginning balance (in shares) | shares 447,049
Granted (in shares) | shares 242,201
Vested (in shares) | shares (83,571)
Canceled (in shares) | shares (516)
Ending balance (in shares) | shares 605,163
WEIGHTED AVERAGE FAIR VALUE PER SHARE  
Beginning balance (in dollars per share) | $ / shares $ 41.08
Granted (in dollars per share) | $ / shares 55.45
Vested (in dollars per share) | $ / shares 32.13
Canceled (in dollars per share) | $ / shares 56.25
Ending balance (in dollars per share) | $ / shares $ 48.05