Convertible Preferred Stock (Parenthetical) (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Class of Stock [Line Items]
Preferred stock, par value	$ 0.01	$ 0.01
Total preferred stock shares authorized for issuance	61,617,516	61,617,516
Preferred stock, shares authorized	61,617,516
Series A Convertible Preferred Stock
Class of Stock [Line Items]
Total preferred stock shares authorized for issuance	17,006,275
Preferred stock, shares authorized	17,006,275	17,006,275
Convertible Preferred Stock Issued	16,525,086	16,317,747
Preferred stock, shares outstanding	16,525,086	16,317,747
Preferred stock, aggregate liquidation preference	$ 17,599	$ 17,371
Series B Convertible Preferred Stock
Class of Stock [Line Items]
Total preferred stock shares authorized for issuance	16,410,526
Preferred stock, shares authorized	16,410,526	16,410,526
Convertible Preferred Stock Issued	16,394,324	16,394,324
Preferred stock, shares outstanding	16,394,324	16,394,324
Preferred stock, aggregate liquidation preference	12,167	12,167
Series C Convertible Preferred Stock
Class of Stock [Line Items]
Total preferred stock shares authorized for issuance	15,621,609
Preferred stock, shares authorized	15,621,609	15,621,609
Convertible Preferred Stock Issued	15,621,609	15,621,609
Preferred stock, shares outstanding	15,621,609	15,621,609
Preferred stock, aggregate liquidation preference	24,490	24,490
Series D Convertible Preferred Stock
Class of Stock [Line Items]
Total preferred stock shares authorized for issuance	9,007,678
Preferred stock, shares authorized	9,007,678	9,007,678
Convertible Preferred Stock Issued	9,007,678	9,007,678
Preferred stock, shares outstanding	9,007,678	9,007,678
Preferred stock, aggregate liquidation preference	32,044	32,044
Series E Convertible Preferred Stock
Class of Stock [Line Items]
Total preferred stock shares authorized for issuance	3,571,428
Preferred stock, shares authorized	3,571,428	3,571,428
Convertible Preferred Stock Issued	2,500,000	2,500,000
Preferred stock, shares outstanding	2,500,000	2,500,000
Preferred stock, aggregate liquidation preference	$ 17,500	$ 17,500