Segment Reporting - Assets by Geographic Region (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Revenues from External Customers and Long-Lived Assets [Line Items]
Fixed Assets	$ 294,003	$ 307,838
Total Assets	641,934	634,749
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Fixed Assets	290,324	304,807
Total Assets	622,836	617,050
Canada
Revenues from External Customers and Long-Lived Assets [Line Items]
Fixed Assets	3,679	3,031
Total Assets	$ 19,098	$ 17,699