Summary of Significant Accounting Policies - Property, Plant and Equipment (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 187,603	$ 180,341
Less accumulated depreciation	(70,034)	(68,854)
Property plant and equipment net excluding capitalized cost	117,569	111,487
Construction in progress	1,601	703
Property, Plant and Equipment, net	119,170	112,190
Land [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 50,689	45,928
Estimated useful life	Indefinite
Land Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 43,337	42,677
Land Improvements [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	20 years
Land Improvements [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	50 years
Buildings [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 26,862	26,105
Estimated useful life	30 years
Furniture, Office and Computer Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 32,118	35,215
Furniture, Office and Computer Equipment [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	3 years
Furniture, Office and Computer Equipment [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	10 years
Vehicles and Machinery [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 34,597	$ 30,416
Vehicles and Machinery [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	5 years
Vehicles and Machinery [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	25 years