Property and Equipment, Net - Schedule of Property and Equipment (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Total, at cost	$ 25,482	$ 24,057
Less: accumulated depreciation and amortization	7,002	5,309
Property and equipment, net	18,480	18,748
Land [Member]
Property, Plant and Equipment [Line Items]
Total, at cost	2,582	2,582
Building [Member]
Property, Plant and Equipment [Line Items]
Total, at cost	12,102	12,148
Computer Hardware and Software [Member]
Property, Plant and Equipment [Line Items]
Total, at cost	4,519	4,093
Office Furniture and Equipment [Member]
Property, Plant and Equipment [Line Items]
Total, at cost	1,058	759
Tenant and Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Total, at cost	4,341	3,660
Vehicle Fleet [Member]
Property, Plant and Equipment [Line Items]
Total, at cost	$ 880	$ 815