Employee Benefit Plans - Net Periodic Pension and Postretirement Benefit Costs (Details) - Pension Plans, Defined Benefit [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service costs	$ 1,120	$ 1,150	$ 950
Interest costs	1,100	1,290	1,510
Expected return on plan assets	(1,520)	(1,480)	(1,610)
Settlements and curtailments loss	2,620	0	1,330
Amortization of net (gain)/loss	860	1,010	930
Net periodic benefit cost (income)	4,180	$ 1,970	$ 3,110
Domestic Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Settlements and curtailments loss	$ 2,500