Property and Equipment, Net - Summary of Depreciation Expense Related to Property and Equipment (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Property, Plant and Equipment [Line Items]
Total depreciation expense	$ 5,353us-gaap_Depreciation	$ 4,756us-gaap_Depreciation	$ 4,688us-gaap_Depreciation
Operating Expenses [Member]
Property, Plant and Equipment [Line Items]
Total depreciation expense	4,940	4,425	4,381
Corporate General and Administrative Expenses [Member]
Property, Plant and Equipment [Line Items]
Total depreciation expense	$ 413	$ 331	$ 307