Securitization Activities and Variable Interest Entities (Details) (USD $)	9 Months Ended	11 Months Ended					3 Months Ended	9 Months Ended
	Aug. 31, 2011	Nov. 30, 2010	Aug. 31, 2011 Residential mortgage-backed securities [Member]	Nov. 30, 2010 Residential mortgage-backed securities [Member]	Aug. 31, 2011 Commercial mortgage-backed securities [Member]	Nov. 30, 2010 Commercial mortgage-backed securities [Member]	Nov. 30, 2010 Loans Payable [Member]	Aug. 31, 2011 Loans Payable [Member]	Sep. 30, 2011 Current year securities [Member]	Sep. 30, 2010 Previous year securities [Member]
Table showing total information regarding securitization vehicles
Assets obtained as proceeds			$ 1,490,100,000	$ 2,203,100,000	$ 134,200,000	$ 105,700,000	$ 100,000	$ 300,000
Total RMBS securitization assets	7,097,200,000	6,549,500,000
Fair Value of Mortgage-Backed Securitizations Initially Retained			679,800,000	684,700,000	73,000,000	40,400,000
Total CMBS securitization assets	3,076,400,000	2,005,400,000
Total project loan assets	90,000,000	107,800,000
Assets Retained	347,000	87,000					100,000	300,000
Securitization Activities and Variable Interest Entities (Textuals) [Abstract]
Inventory in residential mortgage-backed securities									403,900,000	60,900,000
Inventory in Commercial mortgage-backed securities									$ 53,400,000	$ 28,600,000