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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, 2017
Jun. 30, 2016
Jun. 30, 2017
Jun. 30, 2016
Property, Plant and Equipment [Line Items]        
Total depreciation expense $ 5,638 $ 5,437 $ 11,279 $ 10,682
Operating Expenses [Member]        
Property, Plant and Equipment [Line Items]        
Total depreciation expense 5,546 5,322 11,089 10,452
Corporate General and Administrative Expenses [Member]        
Property, Plant and Equipment [Line Items]        
Total depreciation expense $ 92 $ 115 $ 190 $ 230