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Stock-Based Compensation - Summary of Restricted Stock and Restricted Stock Units (Details) - Restricted stock and restricted stock units
shares in Thousands
3 Months Ended
Mar. 31, 2018
$ / shares
shares
Shares  
December 31, 2017 (in shares) | shares 145
Granted (in shares) | shares 139
Vested (in shares) | shares (34)
Forfeited (in shares) | shares (2)
March 31, 2018 (in shares) | shares 248
Weighted Average Grant Date Fair Value  
December 31, 2017 (in dollars per share) | $ / shares $ 37.07
Granted (in dollars per share) | $ / shares 52.06
Vested (in dollars per share) | $ / shares 35.16
Forfeited (in dollars per share) | $ / shares 52.06
March 31, 2018 (in dollars per share) | $ / shares $ 45.64