Segment Reporting - Long-lived Assets by Geographic Region (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment reporting
Long-lived Assets	$ 120,376	$ 126,090	$ 133,971
U.S. Operations
Segment reporting
Long-lived Assets	86,345	92,509	97,226
Canadian Operations
Segment reporting
Long-lived Assets	3,841	6,972	6,357
Europe
Segment reporting
Long-lived Assets	26,130	22,883	27,226
Asia Pacific Operations
Segment reporting
Long-lived Assets	$ 4,060	$ 3,726	$ 3,162