Depreciation and Amortization - Depreciation and Amortization Expense for Property and Equipment and Intangible Assets (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Property, Plant and Equipment [Line Items]
Total depreciation and amortization expense	$ 5,317	$ 5,901	$ 10,976	$ 11,676
Operating Expenses [Member]
Property, Plant and Equipment [Line Items]
Total depreciation and amortization expense	5,282	5,825	10,906	11,507
Corporate General and Administrative Expenses [Member]
Property, Plant and Equipment [Line Items]
Total depreciation and amortization expense	$ 35	$ 76	$ 70	$ 169