Preferred Stock - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	6 Months Ended
	Jun. 30, 2013 Director Vote
Class of Stock [Line Items]
Percentage of voting power threshold for payment of liquidation preference	50.00%
Majority of outstanding shares of convertible preferred stock	55.00%
Proceeds from public offering of common stock	$ 30.0
Preferred stock conversion into number of common share	1
Non cumulative dividends rate	6.00%
Preferred stockholder's number of vote for each share of common stock	1
Number of board of directors common stockholders are entitled to elect	1
Series A Convertible Preferred Stock
Class of Stock [Line Items]
Convertible preferred stock, liquidation preference	$ 1.0650
Number of Board of Directors convertible preferred stockholders are entitled to elect	2
Series B Convertible Preferred Stock
Class of Stock [Line Items]
Convertible preferred stock, liquidation preference	$ 0.7483
Number of Board of Directors convertible preferred stockholders are entitled to elect	1
Series C Convertible Preferred Stock
Class of Stock [Line Items]
Convertible preferred stock, liquidation preference	$ 1.5677
Number of Board of Directors convertible preferred stockholders are entitled to elect	0
Series D Convertible Preferred Stock
Class of Stock [Line Items]
Convertible preferred stock, liquidation preference	$ 3.5570
Number of Board of Directors convertible preferred stockholders are entitled to elect	0
Series E Convertible Preferred Stock
Class of Stock [Line Items]
Convertible preferred stock, liquidation preference	$ 7.0000
Number of Board of Directors convertible preferred stockholders are entitled to elect	1