Convertible Preferred Stock (Details 3) (USD $) In Thousands, except Share data, unless otherwise specified			1 Months Ended
	Dec. 31, 2012	Apr. 30, 2012 Series B Preferred Stock	Apr. 30, 2012 Initial public offering Common stock
Convertible preferred stock
Convertible preferred stock converted into common stock (in shares)			66,255,529
Accrued dividends on preferred stock paid in cash	$ 28	$ 4,300