Common Stock and Preferred Stock - Summary of Future Issuance of Common Stock Shares (Detail) In Thousands, unless otherwise specified	Dec. 31, 2013
Common And Preferred Stock [Line Items]
Reserved for future issuance of common stock	5,296
Restricted Stock [Member]
Common And Preferred Stock [Line Items]
Reserved for future issuance of common stock	69
Options to Purchase Common Stock [Member]
Common And Preferred Stock [Line Items]
Reserved for future issuance of common stock	4,651
Warrants to Purchase Common Stock [Member]
Common And Preferred Stock [Line Items]
Reserved for future issuance of common stock	338
Employee Stock Purchase Plan [Member]
Common And Preferred Stock [Line Items]
Reserved for future issuance of common stock	238