Summary of Significant Accounting Policies - Property and Equipment (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 21,196	$ 19,470
Less: accumulated depreciation and amortization	(11,739)	(10,653)
Property and equipment, net	9,457	8,817
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	848	1,277
Computer Equipment and Software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	4,026	4,014
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	1,294	1,362
Internal-use Software and Website Development Costs [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 15,028	$ 12,817