Stock-Based Compensation - RSUs and PSUs (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Restricted stock units
Number of RSUs
Balance at the beginning of the period (in shares)	270,052
Granted (in shares)	77,214
Forfeited (in shares)	(1,500)
Vested (in shares)	(77,260)
Balance at the end of the period (in shares)	268,506
Weighted Average Grant Date Fair Value
Balance at the beginning of the year (in dollars per shares)	$ 41.70
Granted (in dollars per share)	51.18
Forfeited (in dollars per share)	39.94
Vested (in dollars per share)	26.71
Balance at the end of the year (in dollars per shares)	$ 48.75
Aggregate market value of RSUs vested	$ 4,135	$ 11,554
PSUs
Number of RSUs
Balance at the beginning of the period (in shares)	90,020
Granted (in shares)	51,839
Forfeited (in shares)	0
Vested (in shares)	0
Balance at the end of the period (in shares)	141,859
Weighted Average Grant Date Fair Value
Balance at the beginning of the year (in dollars per shares)	$ 55.06
Granted (in dollars per share)	60.36
Forfeited (in dollars per share)	0
Vested (in dollars per share)	0
Balance at the end of the year (in dollars per shares)	$ 57.00