Convertible Preferred Stock (Details) (USD $)	3 Months Ended
	Mar. 31, 2012
Convertible Preferred Stock [Abstract]
Convertible preferred stock, interest rate, stated percentage	5.25%
Convertible Preferred Stock, Prior Conversion Ratio	74.4500
Convertible Preferred Stock, Current Conversion Ratio	75.3568
Convertible Preferred Stock, Prior Conversion Price	$ 13.43
Convertible Preferred Stock, Current Conversion Price	$ 13.27