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Stock-based Compensation - Summary of Non-Vested Restricted Common Shares (Details) - 2013 Plan - Restricted common shares - $ / shares
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Shares      
Non-vested at the beginning of the period (in shares) 173,276 296,785 311,839
Granted (in shares) 206,446 143,593 155,306
Vested (in shares) (153,325) (266,552) (170,034)
Forfeited (in shares) (1,258) (550) (326)
Non-vested at the end of the period (in shares) 225,139 173,276 296,785
Weighted Average Grant Date Fair Value      
Non-vested at beginning of period (in dollars per share) $ 19.36 $ 16.16 $ 14.17
Granted (in dollars per share) 14.87 19.74 17.96
Vested (in dollars per share) 19.32 16.00 14.16
Forfeited (in dollars per share) 16.27 18.78 15.36
Non-vested at end of period (in dollars per share) $ 15.29 $ 19.36 $ 16.16