Employee Benefits - Benefit Obligation Rollforward (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Change in Benefit Obligation
Benefit obligation at the beginning of the period	$ 18,927	$ 20,793	$ 21,304
Service cost	335	367	340
Interest cost	658	600	711
Payments	(1,913)	(1,913)	(1,913)
Actuarial (gain) loss	1,207	(920)	351
Benefit obligation at the end of the period	$ 19,214	$ 18,927	$ 20,793