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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 9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Property, Plant and Equipment [Line Items]        
Total depreciation expense $ 5,888 $ 5,677 $ 17,167 $ 16,359
Operating Expenses [Member]        
Property, Plant and Equipment [Line Items]        
Total depreciation expense 5,796 5,569 16,885 16,021
Corporate General and Administrative Expenses [Member]        
Property, Plant and Equipment [Line Items]        
Total depreciation expense $ 92 $ 108 $ 282 $ 338