Pension Plans - Periodic Pension Cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Retirement Benefits [Abstract]
Service cost	$ 0	$ 0	$ 0
Interest cost	4	5	11
Other	0	0	0
Curtailment/settlement (gain) loss	0	0	0
Net periodic pension costs	$ 4	$ 5	$ 11