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Share-Based Compensation - Stock Options - (Details) - USD ($)
$ / shares in Units, $ in Thousands
3 Months Ended
Jan. 27, 2012
Mar. 31, 2018
Aggregate Intrinsic Value    
Outstanding at the end of the period   $ 7,194
Exercisable at the end of the period   $ 6,767
Stock Options    
Number of shares    
Outstanding at the beginning of the period (in shares)   218,689
Granted (in shares)   34,407
Exercised (in shares)   (2,240)
Forfeited (in shares)   (5,806)
Outstanding at the end of the period (in shares)   245,050
Exercisable at the end of the period (in shares)   171,299
Weighted-Average Exercise Price    
Outstanding at the beginning of the period (in dollars per share)   $ 52.75
Granted (in dollars per share)   91.05
Exercised (in dollars per share)   29.95
Forfeited (in dollars per share)   91.35
Outstanding at the end of the period (in dollars per share)   57.42
Exercisable at the end of the period (in dollars per share)   46.05
Weighted-average fair value of options granted during the year (in dollars per share)   $ 28.01
Weighted-Average Remaining Contractual Life    
Outstanding at the end of the period   5 years 9 months 11 days
Exercisable at the end of the period   4 months 13 days
2012 plan    
Share-Based Compensation    
Number of shares registered under the 2012 plan   1,684,000
2012 plan | Restricted Stock. | Maximum    
Share-Based Compensation    
Number of shares registered under the 2012 plan   817,476
2004 plan    
Number of shares    
Granted (in shares) 0  
Plan 2004 And 2012 | Incentive stock options    
Share-Based Compensation    
Vesting percentage   25.00%
Expiration period   10 years
Plan 2004 And 2012 | Incentive stock options | Maximum    
Share-Based Compensation    
Vesting period   4 years