Employee Benefit Plans - Defined Benefit Pension Plann (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Benefit obligation assumptions
Discount rate ( as a percentage)	0.75%	0.75%
Rate of compensation increase ( as a percentage)	2.00%	1.50%
Expected return on plan assets (as a percentage)	0.75%	0.75%
Periodic benefit cost assumptions
Discount rate ( as a percentage)	0.75%	0.75%
Rate of compensation increase ( as a percentage)	1.50%	1.50%
Expected return on plan assets (as a percentage)	0.75%	0.75%
Changes in the obligations
Benefit obligation, beginning of the year	$ 23,787
Benefit obligations acquired / established		$ 17,591
Service cost	2,836	1,225
Interest cost	190	76
Plan participants contributions	1,101	536
Actuarial loss	4,514	2,249
Plan change	1,430
Benefit payments from fund	2,853	2,548
Expenses paid from assets	36	20
Translation gain (loss)	909	(418)
Benefit obligation, end of the year	37,584	23,787
Changes in plan assets
Fair value of plan assets, beginning of year	16,699
Fair value of plan assets acquired / established		12,598
Actual return on plan assets	88	100
Employer contributions	2,891	1,323
Plan participants contributions	1,101	536
Benefit payments from fund	2,853	2,548
Expenses paid from assets	36	20
Translation gain (loss)	595	(386)
Fair value of plan assets, end of year	24,191	16,699
Unfunded liability, end of year	13,393	7,088
Accumulated benefit obligation	$ 33,100	$ 22,600