Convertible Preferred Stock (Parenthetical) (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Class of Stock [Line Items]
Preferred stock, par value	$ 0.01	$ 0.01
Total preferred stock shares authorized for issuance	125,307,087	123,235,032
Series A Convertible Preferred Stock
Class of Stock [Line Items]
Convertible preferred stock, shares authorized	33,825,798	34,012,550
Convertible preferred stock, shares issued	33,050,172	33,050,172
Convertible preferred stock, shares outstanding	33,050,172	33,050,172
Convertible preferred stock, aggregate liquidation preference	$ 17,599	$ 17,599
Series B Convertible Preferred Stock
Class of Stock [Line Items]
Convertible preferred stock, shares authorized	32,788,650	32,821,052
Convertible preferred stock, shares issued	32,788,650	32,788,650
Convertible preferred stock, shares outstanding	32,788,650	32,788,650
Convertible preferred stock, aggregate liquidation preference	12,268	12,268
Series C Convertible Preferred Stock
Class of Stock [Line Items]
Convertible preferred stock, shares authorized	31,243,218	31,243,218
Convertible preferred stock, shares issued	31,243,218	31,243,218
Convertible preferred stock, shares outstanding	31,243,218	31,243,218
Convertible preferred stock, aggregate liquidation preference	24,490	24,490
Series D Convertible Preferred Stock
Class of Stock [Line Items]
Convertible preferred stock, shares authorized	18,015,356	18,015,356
Convertible preferred stock, shares issued	18,015,356	18,015,356
Convertible preferred stock, shares outstanding	18,015,356	18,015,356
Convertible preferred stock, aggregate liquidation preference	32,044	32,044
Series E Convertible Preferred Stock
Class of Stock [Line Items]
Convertible preferred stock, shares authorized	5,000,000	7,142,856
Convertible preferred stock, shares issued	5,000,000	5,000,000
Convertible preferred stock, shares outstanding	5,000,000	5,000,000
Convertible preferred stock, aggregate liquidation preference	17,500	17,500
Series F Convertible Preferred Stock
Class of Stock [Line Items]
Preferred stock, par value	$ 0.01
Convertible preferred stock, shares authorized	4,434,065
Convertible preferred stock, shares issued	4,417,243
Convertible preferred stock, shares outstanding	4,417,243
Convertible preferred stock, aggregate liquidation preference	$ 89,858