Stock-Based Compensation - Activity of stock incentive plans for options (Details) $ / shares in Units, $ in Thousands	6 Months Ended
	Jun. 30, 2020 USD ($) $ / shares shares
Option Shares Outstanding
Forfeited (in shares)	(17,699)
Stock Incentive Plan | Stock Options
Option Shares Outstanding
Beginning balance outstanding (in shares)	1,443,733
Granted (in shares)	39,500
Exercise of stock options (in shares)	(43,552)
Forfeited (in shares)	0
Ending balance outstanding (in shares)	1,439,681
Exercisable (in shares)	726,931
Weighted Average Exercise Price
Beginning balance outstanding (in usd per share) | $ / shares	$ 48.75
Granted (in usd per share) | $ / shares	71.89
Exercise of stock options (in usd per share) | $ / shares	23.07
Forfeited (in usd per share) | $ / shares	0
Ending balance outstanding (in usd per share) | $ / shares	50.16
Exercisable (in usd per share) | $ / shares	$ 44.59
Weighted average remaining life outstanding (in years)	7 years 1 month 6 days
Weighted average remaining life exercisable (in years)	6 years 4 months 24 days
Aggregate intrinsic value outstanding | $	$ 10,601
Aggregate intrinsic value exercisable | $	$ 7,527