Defined Benefit Plans - Net Periodic Pension Costs (Details) - Pension Plans, Defined Benefit [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service costs	$ 330	$ 320	$ 980	$ 950
Interest costs	200	240	600	710
Expected return on plan assets	(380)	(380)	(1,160)	(1,110)
Amortization of net (gain)/loss	220	220	680	670
Net periodic benefit cost	$ 370	$ 400	$ 1,100	$ 1,220