Other Employee Benefit Plans (Details 3) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Change in benefit obligation:
Benefit obligation at January 1	$ 11,426	$ 11,813
Service costs	0	156	$ 166
Interest costs	397	353	444
Actuarial loss (gain)	177	(199)
Benefits paid	(312)	(312)
Foreign currency exchange changes	(269)	(385)
Benefit obligation at December 31	11,419	11,426	$ 11,813
Fair value of plan assets at December 31	0	0
Unfunded status at December 31	11,419	11,426
Amounts recognized in the Consolidated Balance Sheets:
Current liabilities	292	307
Non-current liabilities	$ 11,127	$ 11,119
Supplemental Executive Retirement Plan (SERP)
Net periodic benefit cost:
Discount rate	4.00%	3.75%
Rate of increase in compensation levels	3.00%	3.00%
Funded status and projected benefit obligation:
Discount rate	4.00%	4.00%
Rate of increase in compensation levels	3.00%	3.00%
Defined benefit pension plan for employees outside the United States
Net periodic benefit cost:
Discount rate	2.00%	2.60%
Funded status and projected benefit obligation:
Discount rate	2.00%	2.60%