Employee Benefit Plans - Net Periodic Pension and Postretirement Benefit Costs (Details) - Pension Plans, Defined Benefit [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service costs	$ 1,230	$ 1,050	$ 1,120
Interest costs	930	1,070	1,100
Expected return on plan assets	(1,450)	(1,400)	(1,520)
Settlements and curtailments loss	0	0	2,620
Amortization of net (gain)/loss	890	580	860
Net periodic benefit cost (income)	$ 1,600	1,300	$ 4,180
United States
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Settlements and curtailments loss		$ 2,500