Initial Public Offering (Details) (Initial public offering, USD $) In Millions, except Share data, unless otherwise specified	1 Months Ended
	Apr. 30, 2012
Public Offering
Convertible preferred stock converted into common stock (in shares)	66,255,529
Cash dividends payable to Series B convertible preferred stock holders	$ 4.3
Common stock
Public Offering
Aggregate shares of common stock sold in connection with initial public offering	15,042,459
Public offering price (in dollars per share)	$ 7.00
Common stock issued to underwriters under an over-allotment option (in shares)	742,459
Net proceeds from initial public offering	$ 98.1