Stock Plans and Stock Based Compensation - Activity Related to Restricted Stock Awards (Details)	12 Months Ended
	Dec. 31, 2018 $ / shares shares
Number of Shares
Unvested, beginning of year (in shares) | shares	261,373
Granted (in shares) | shares	65,785
Vested (in shares) | shares	(53,667)
Forfeited (in shares) | shares	(18,252)
Unvested, end of year (in shares) | shares	255,239
Weighted Average Fair Value
Beginning balance (in dollars per share) | $ / shares	$ 61.32
Granted (in dollars per share) | $ / shares	75.44
Vested (in dollars per share) | $ / shares	53.71
Forfeited (in dollars per share) | $ / shares	61.81
Ending balance (in dollars per share) | $ / shares	$ 66.52