Defined Benefit Plans - Net Periodic Pension and Postretirement Benefit Costs (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Pension Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service costs	$ 240	$ 230	$ 490	$ 470
Interest costs	390	410	790	830
Expected return on plan assets	(420)	(490)	(840)	(1,010)
Amortization of prior service cost	10	10	10	10
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Settlements and Curtailments	0	(2,750)	0	(2,750)
Amortization of net (gain)/loss	240	360	470	740
Net periodic benefit cost	460	3,270	920	3,790
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service costs	0	0	0	0
Interest costs	10	0	10	10
Expected return on plan assets	0	0	0	0
Amortization of prior service cost	0	0	0	0
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Settlements and Curtailments	0	0	0	0
Amortization of net (gain)/loss	(20)	(10)	(30)	(20)
Net periodic benefit cost	$ (10)	$ (10)	$ (20)	$ (10)