Mandatorily Redeemable Convertible Preferred Stock (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended	8 Months Ended	9 Months Ended
	Aug. 31, 2011	Aug. 31, 2010	Aug. 31, 2011	Aug. 31, 2011 Series A Preferred Stock [Member]	Feb. 28, 2006 Series A Preferred Stock [Member]
Dividends Payable [Line Items]
Purchase of Series A convertible preferred stock					$ 125.0
Dividend of Series A convertible preferred stock				0.0325
Number of common stock shares to which Series A preferred stock is convertible	4,110,000	4,105,000	4,108,000	4,110,128
Mandatorily Redeemable Convertible Preferred Stock (Textuals) [Abstract]
Effective conversion price per share	$ 30.41		$ 30.41
Mandatory redeemable preferred stock price per share	$ 1,000		$ 1,000
Preferred stock, shares authorized	10,000,000		10,000,000
Preferred stock, shares issued	125,000		125,000
Preferred stock, shares outstanding	125,000		125,000