Depreciation and Amortization - Depreciation and Amortization Expense for Property and Equipment and Intangible Assets (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Property, Plant and Equipment [Line Items]
Total depreciation and amortization expense	$ 4,770	$ 4,212	$ 14,144	$ 12,473
Operating expenses [Member]
Property, Plant and Equipment [Line Items]
Total depreciation and amortization expense	4,686	4,130	13,911	12,223
Corporate general and administrative expenses [Member]
Property, Plant and Equipment [Line Items]
Total depreciation and amortization expense	$ 84	$ 82	$ 233	$ 250