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, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Property, Plant and Equipment [Line Items]
Total depreciation and amortization expense	$ 5,117	$ 5,042	$ 15,168	$ 14,560
Operating Expenses [Member]
Property, Plant and Equipment [Line Items]
Total depreciation and amortization expense	5,000	4,941	14,847	14,226
Corporate General and Administrative Expenses [Member]
Property, Plant and Equipment [Line Items]
Total depreciation and amortization expense	$ 117	$ 101	$ 321	$ 334