Defined Benefit Plans - Net Periodic Pension and Postretirement Benefit Costs (Details) - Pension Plans, Defined Benefit [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service costs	$ 290	$ 250	$ 840	$ 740
Interest costs	310	390	950	1,180
Expected return on plan assets	(370)	(420)	(1,100)	(1,260)
Amortization of net (gain)/loss	260	230	760	710
Net periodic benefit cost	$ 490	$ 450	$ 1,450	$ 1,370