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, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Property, Plant and Equipment [Line Items]
Total depreciation and amortization expense	$ 5,064	$ 4,818	$ 10,051	$ 9,518
Operating Expenses [Member]
Property, Plant and Equipment [Line Items]
Total depreciation and amortization expense	4,956	4,701	9,847	9,285
Corporate General and Administrative Expenses [Member]
Property, Plant and Equipment [Line Items]
Total depreciation and amortization expense	$ 108	$ 117	$ 204	$ 233