Employee Benefit Plans - Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Pension Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost			$ 0
Interest cost			36
Expected return on assets			(45)
Amortization of prior service cost			0
Recognized net actuarial loss			25
Settlement losses			414
Net benefit cost (benefit)			430
Post-employment benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 25	$ 36	51
Interest cost	122	142	141
Expected return on assets	0	0	0
Amortization of prior service cost	(339)	(338)	(338)
Recognized net actuarial loss	184	269	278
Settlement losses	0	0	0
Net benefit cost (benefit)	$ (8)	$ 109	$ 132