Defined Benefit Plans - Net Periodic Pension Costs (Details) - Pension Plans, Defined Benefit [Member] - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service costs	$ 320	$ 310	$ 650	$ 630
Interest costs	200	230	400	470
Expected return on plan assets	(390)	(360)	(780)	(730)
Amortization of net (gain)/loss	230	230	460	450
Net periodic benefit cost	$ 360	$ 410	$ 730	$ 820