Cash, cash equivalents and restricted cash (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2015
Cash and cash equivalents	$ 69,429	$ 70,791	$ 67,571
Long-term restricted cash	6,792		6,863
Total cash, cash equivalents and long-term restricted cash	76,221	$ 77,655	74,434	$ 85,825
Workers' Compensation Liability	800		900
Deposit related to customs activity	100		100
Revolving credit facility
Availability used to support outstanding letters of credit	6,800		6,900
Revolving credit facility | Sale leaseback obligation
Security Deposit	$ 5,900		$ 5,900