Defined Benefit Plans - Net Periodic Pension and Postretirement Benefit Costs (Details) - Pension Plans, Defined Benefit [Member] - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service costs	$ 270	$ 240	$ 550	$ 490
Interest costs	320	390	640	790
Expected return on plan assets	(360)	(420)	(730)	(840)
Amortization of net (gain)/loss	250	250	500	480
Net periodic benefit cost	$ 480	$ 460	$ 960	$ 920