Annual report pursuant to Section 13 and 15(d)

Stock Based Compensation - Summary of Restricted Stock Awards and Units (Details)

v3.8.0.1
Stock Based Compensation - Summary of Restricted Stock Awards and Units (Details) - USD ($)
$ / shares in Units, $ in Thousands
 3 Months Ended 12 Months Ended
Mar. 31, 2017
Mar. 31, 2016
Mar. 31, 2015
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Stock-based compensation              
Proceeds from exercise of stock options           $ 111  
Common Stock              
Options              
Exercised (in shares)           26,350  
A&R 2004 Plan | Common Stock              
Stock-based compensation              
Shares reserved for issuance       0      
2010 Plan | Common Stock              
Stock-based compensation              
Maximum number of shares of common stock that may be issued       2,130,000      
Number of shares of common stock available for grant       1,147,750      
Restricted Stock Share Awards              
Shares              
Unvested at the beginning of the period (in shares)   14,701 85,021   14,701 85,021  
Vested (in shares)         (14,701) (70,320)  
Unvested at the end of the period (in shares)           14,701 85,021
Weighted Average Grant Date Fair Value              
Unvested at the beginning of the period (in dollars per share)   $ 14.78 $ 13.02   $ 14.78 $ 13.02  
Vested (in dollars per share)         $ 14.78 12.65  
Unvested at the end of the period (in dollars per share)           $ 14.78 $ 13.02
Weighted Average Remaining Contractual Term              
Unvested at the beginning of the period           4 days 6 months 4 days
Unvested at the end of the period           4 days 6 months 4 days
Restricted Stock Unit Awards              
Shares              
Unvested at the beginning of the period (in shares) 47,790 48,665 81,623 47,790 48,665 81,623  
Granted (in shares)       128,893 131,765 116,141  
Vested (in shares)       (128,697) (132,640) (147,217)  
Cancelled and forfeited (in shares)       (444)   (1,882)  
Unvested at the end of the period (in shares)       47,542 47,790 48,665 81,623
Expected to vest in the future, at the end of the period (in shares)       45,830      
Weighted Average Grant Date Fair Value              
Unvested at the beginning of the period (in dollars per share) $ 20.31 $ 17.33 $ 15.05 $ 20.31 $ 17.33 $ 15.05  
Granted (in dollars per share) $ 33.60 $ 19.88 $ 22.63 24.31 21.37 18.72  
Vested (in dollars per share)       22.93 20.27 16.51  
Cancelled and forfeited (in dollars per share)       33.60   15.82  
Unvested at the end of the period (in dollars per share)       23.95 $ 20.31 $ 17.33 $ 15.05
Expected to vest in the future, at the end of the period (in dollars per share)       $ 23.95      
Weighted Average Remaining Contractual Term              
Unvested at the beginning of the period       10 months 2 days 11 months 16 days 1 year 1 year 1 month 2 days
Granted       3 months 22 days 4 months 6 days 4 months 24 days  
Unvested at the end of the period       10 months 2 days 11 months 16 days 1 year 1 year 1 month 2 days
Expected to vest in future, at the end of the period       10 months 2 days      
Stock Options | A&R 2004 Plan              
Stock-based compensation              
Proceeds from exercise of stock options           $ 111  
Options              
Outstanding stock options       0 0    
Exercised (in shares)       0 0 26,350  
Cancelled (in shares)           10,890