v3.8.0.1
Stock-Based Compensation - Summary of Stock Appreciation Rights Activity (Details)
$ / shares in Units, $ in Thousands
 12 Months Ended
Dec. 31, 2017
USD ($)
$ / shares
shares
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]  
Vested and exercisable (in shares) 146,899
Stock appreciation rights (“SARs”)  
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]  
Beginning balance (in shares) 226,500
Granted (in shares) 174,500
Exercised (in shares) (21,300)
Forfeited/Canceled (in shares) (12,800)
Ending balance (in shares) 366,900
Vested and exercisable (in shares) 67,200
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]  
Beginning balance (in dollars per share) | $ / shares $ 37.97
Granted (in dollars per share) | $ / shares 41.95
Exercised (in dollars per share) | $ / shares 38.49
Forfeited/Canceled (in dollars per share) | $ / shares 41.36
Ending balance (in dollars per share) | $ / shares 39.73
Vested and exercisable (in dollars per share) | $ / shares $ 39.87
Outstanding, weighted average contractual term (in years) 8 years 2 months 12 days
Vested and exercisable, weighted average contractual term (in years) 7 years
Outstanding, aggregate intrinsic value | $ $ 3,274
Vested and exercisable, aggregate intrinsic value | $ $ 590