Commitments and Contingencies - Total Rent Expense Under Operating Lease (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating Leases [Line Items]
Rent expense under operating leases	$ 7,871	$ 7,171	$ 6,343
Cost of Sales [Member]
Operating Leases [Line Items]
Rent expense under operating leases	733	573	435
Selling and Marketing Expense [Member]
Operating Leases [Line Items]
Rent expense under operating leases	34	32	113
Administrative [Member]
Operating Leases [Line Items]
Rent expense under operating leases	$ 7,104	$ 6,566	$ 5,795