Segment Reporting (Detail) - Long-lived Asset Information By Location (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	$ 4,151	$ 4,667
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	4,137	4,646
Japan
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	$ 14	$ 21