Stockholders' Equity (Details) (USD $)	12 Months Ended			2 Months Ended	12 Months Ended			0 Months Ended		1 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013 7.50% Convertible Senior Secured Notes due 2019	Dec. 31, 2013 7.50% Convertible Senior Secured Notes due 2019	Dec. 31, 2013 Series A Preferred Stock	May 31, 2012 Series A Preferred Stock	Dec. 05, 2012 Common Stock	May 01, 2012 Common Stock	Jan. 31, 2013 Common Stock	Dec. 31, 2013 Common Stock item	May 31, 2012 Common Stock
Stockholders' equity
Number of outstanding shares of Series A preferred Stock that are automatically converted to shares of common stock							49,000,000
Number of shares of common stock into which Series A preferred stock automatically got converted												12,249,998
Rate at which dividends accrued (in dollars per share)						$ 0.07
Amount of dividends paid prior to the conversion of the preferred stock into common stock in connection with the IPO						$ 0
Number of votes to which holders of common shares are entitled for each share held											1
Number of shares sold								6,000,000	10,000,000
Selling price (in dollars per share)								$ 8	$ 5	$ 8
Expenses incurred in connection with offering	869,000							3,300,000	4,700,000
Shares of common stock sold upon exercise of full amount of over-allotment option by the underwriters									449,250	239,432
Gross proceeds from issuance of common stock									52,300,000
Net cash proceeds from sale of common stock									47,600,000
Gross cash proceeds from sale of common stock in a follow-on offering	2,437,000	100,735,000	29,000					49,900,000
Net cash proceeds from sale of common stock in a follow-on offering								46,600,000
Shares of common stock issued in conversion of Notes				7,641,060	7,600,000
Principal amount of the Notes converted				$ 40,500,000	$ (40,492,000)
Shares of common stock issued in settlement of the interest make-whole provision				1,337,193	1,300,000