Employee Benefit Plans - Net Periodic Pension and Postretirement Benefit Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Pension Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service costs	$ 890	$ 760	$ 680
Interest costs	1,580	1,760	1,610
Expected return on plan assets	(1,840)	(2,070)	(1,810)
Settlements and curtailments gain	2,750	0	0
Amortization of net (gain)/loss	1,340	1,120	1,280
Net periodic benefit cost (income)	4,720	1,570	1,760
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
Interest costs	20	30	40
Expected return on plan assets	0	0	0
Settlements and curtailments gain	0	0	0
Amortization of net (gain)/loss	(30)	(90)	(80)
Net periodic benefit cost (income)	$ (10)	$ (60)	$ (40)