Employee benefit obligations - Net Funded Status (Details) - 12 months ended Dec. 31, 2015 - USD ($) $ in Thousands	Total	Total
Change in Benefit Obligation
Interest cost	$ 47
Company service cost	312
Employee contributions	189
Prior service cost	158
Benefits paid	4,023
Actuarial loss	1,494
Projected benefit obligation at end of year	6,223
Change in Plan Assets
Actual return on plan assets	(63)
Employer contributions	284
Employee contributions	189
Benefits paid	4,023
Fair value of plan assets at end of year	4,433
Funded Status at End of year
Excess of obligation over assets		$ (1,790)
Change in Accrued Benefit Liability
Company contributions made during year	284
Net periodic benefit cost for year	(404)
Net decrease in accumulated other comprehensive loss	(1,670)
Accrued benefit liability at end of year	(1,790)
Non - current plan assets		4,433
Non - current liability		6,223
Accrued benefit liability at end of year	$ (1,790)	(1,790)
Projected Benefit Payments
2016		8
2017		13
2018		19
2019		25
2020		32
2021 - 2024		$ 264