Subsequent Events (Details) (USD $)	0 Months Ended	12 Months Ended					0 Months Ended
	Sep. 22, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 Preferred stock, Series B	Dec. 31, 2011 Preferred stock, Series B	Jan. 03, 2013 Subsequent Event Preferred stock, Series B
Subsequent Event [Line Items]
Preferred stock redeemed (in shares)							22,695.94
Price of preferred stock redeemed	$ 116,596,111	$ 235,000	$ 126,000	$ 76,000			$ 22,695,940
Preferred Stock, outstanding					90,782.94	90,782.94	68,087
Preferred stock, remaining liquidation amount							$ 68,000,000