Summary of Significant Accounting Policies - Components of Property, Building and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Other Long Term Assets [Line Items]
Property, building and equipment, gross	$ 134,816	$ 90,018
Less accumulated depreciation	55,253	43,565
Property, Plant and Equipment, Net	79,563	46,453
Land
Other Long Term Assets [Line Items]
Property, building and equipment, gross	6,750	2,033
Building and improvements
Other Long Term Assets [Line Items]
Property, building and equipment, gross	35,474	14,166
Transportation equipment
Other Long Term Assets [Line Items]
Property, building and equipment, gross	13,503	11,363
Fixed equipment
Other Long Term Assets [Line Items]
Property, building and equipment, gross	745	780
Office furniture and medical equipment
Other Long Term Assets [Line Items]
Property, building and equipment, gross	$ 78,344	$ 61,676