Depreciation and Amortization - Depreciation and Amortization Expense for Property and Equipment and Intangible Assets (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Property, Plant and Equipment [Line Items]
Total depreciation expense	$ 5,775	$ 5,641
Operating Expenses [Member]
Property, Plant and Equipment [Line Items]
Total depreciation expense	5,682	5,543
Corporate General and Administrative Expenses [Member]
Property, Plant and Equipment [Line Items]
Total depreciation expense	$ 93	$ 98