Securitization Activities and Variable Interest Entities (Details 2) (USD $)	Aug. 31, 2011	Nov. 30, 2010	Aug. 31, 2010	Dec. 31, 2009
Variable Interest Entity Consolidated Carrying Amount Assets And Liabilities [Abstract]
Cash and cash equivalents	$ 2,014,950,000	$ 2,188,998,000	$ 2,089,940,000	$ 1,853,167,000
Total financial instruments owned, at fair value	18,139,946,000	15,941,572,000
Securities borrowed	7,815,663,000	8,152,678,000
Receivables from brokers and dealers	3,743,143,000	2,550,234,000
Other assets	816,573,000	601,799,000
Total assets (including $1,267,051 in 2011 and $1,410,626 in 2010 from VIEs)	45,125,243,000	36,726,543,000	32,672,100,000
Total financial instruments sold, not yet purchased, at fair value	10,320,161,000	9,109,799,000
Brokers, dealers and clearing organizations	2,754,164,000	1,885,357,000
Carrying amount of mandatorily redeemable preferred interests of consolidated subsidiaries	313,095,000	315,885,000
Total liabilities (including $835,852 in 2011 and $1,163,465 in 2010 from VIEs)	41,633,555,000	33,915,578,000
Securitization Activities and Variable Interest Entities (Textuals) [Abstract]
Carrying amount of mandatorily redeemable preferred interests of consolidated subsidiaries	313,095,000	315,885,000
Carrying amount of variable interest as debt, equity and partnership interest	324,900,000	328,200,000
Variable Interest Entity, Primary Beneficiary [Member] | High Yield [Member]
Variable Interest Entity Consolidated Carrying Amount Assets And Liabilities [Abstract]
Cash and cash equivalents	283,700,000	202,600,000
Total financial instruments owned, at fair value	779,200,000	889,800,000
Securities borrowed	238,900,000	455,800,000
Receivables from brokers and dealers	177,800,000	195,500,000
Other assets	24,700,000	11,600,000
Total assets (including $1,267,051 in 2011 and $1,410,626 in 2010 from VIEs)	1,504,300,000	1,755,300,000
Total financial instruments sold, not yet purchased, at fair value	383,600,000	602,600,000
Brokers, dealers and clearing organizations	134,500,000	157,100,000
Carrying amount of mandatorily redeemable preferred interests of consolidated subsidiaries	1,047,900,000	1,047,900,000
Promissory note	0	0
Secured financing	0	0
Other	36,900,000	36,300,000
Total liabilities (including $835,852 in 2011 and $1,163,465 in 2010 from VIEs)	1,602,900,000	1,843,900,000
Securitization Activities and Variable Interest Entities (Textuals) [Abstract]
Carrying amount of mandatorily redeemable preferred interests of consolidated subsidiaries	1,047,900,000	1,047,900,000
Variable Interest Entity, Primary Beneficiary [Member] | Mortgage and Asset-backed Securitizations [Member]
Variable Interest Entity Consolidated Carrying Amount Assets And Liabilities [Abstract]
Cash and cash equivalents	0	0
Total financial instruments owned, at fair value	11,600,000	0
Securities borrowed	0	101,400,000
Receivables from brokers and dealers	0	0
Other assets	0	100,000
Total assets (including $1,267,051 in 2011 and $1,410,626 in 2010 from VIEs)	11,600,000	101,500,000
Total financial instruments sold, not yet purchased, at fair value	0	0
Brokers, dealers and clearing organizations	0	0
Carrying amount of mandatorily redeemable preferred interests of consolidated subsidiaries	0	0
Promissory note	0	0
Secured financing	11,600,000	101,400,000
Other	0	100,000
Total liabilities (including $835,852 in 2011 and $1,163,465 in 2010 from VIEs)	0	101,500,000
Securitization Activities and Variable Interest Entities (Textuals) [Abstract]
Carrying amount of mandatorily redeemable preferred interests of consolidated subsidiaries	0	0
Variable Interest Entity, Primary Beneficiary [Member] | Other [Member]
Variable Interest Entity Consolidated Carrying Amount Assets And Liabilities [Abstract]
Cash and cash equivalents	300,000	0
Total financial instruments owned, at fair value	7,300,000	21,000,000
Securities borrowed	0	0
Receivables from brokers and dealers	0	0
Other assets	0	0
Total assets (including $1,267,051 in 2011 and $1,410,626 in 2010 from VIEs)	7,600,000	21,000,000
Total financial instruments sold, not yet purchased, at fair value	0	0
Brokers, dealers and clearing organizations	0	0
Carrying amount of mandatorily redeemable preferred interests of consolidated subsidiaries	0	0
Promissory note	4,100,000	4,400,000
Secured financing	0	0
Other	300,000	0
Total liabilities (including $835,852 in 2011 and $1,163,465 in 2010 from VIEs)	4,400,000	4,400,000
Securitization Activities and Variable Interest Entities (Textuals) [Abstract]
Carrying amount of mandatorily redeemable preferred interests of consolidated subsidiaries	0	0
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity Consolidated Carrying Amount Assets And Liabilities [Abstract]
Cash and cash equivalents	283,968,000	202,565,000
Total financial instruments owned, at fair value	798,081,000	1,012,079,000
Receivables from brokers and dealers	177,793,000	195,485,000
Other assets	446,000	370,000
Total assets (including $1,267,051 in 2011 and $1,410,626 in 2010 from VIEs)	1,267,051,000	1,410,626,000
Total financial instruments sold, not yet purchased, at fair value	380,869,000	596,044,000
Brokers, dealers and clearing organizations	134,477,000	157,134,000
Carrying amount of mandatorily redeemable preferred interests of consolidated subsidiaries	313,095,000	315,885,000
Total liabilities (including $835,852 in 2011 and $1,163,465 in 2010 from VIEs)	835,852,000	1,163,465,000
Securitization Activities and Variable Interest Entities (Textuals) [Abstract]
Carrying amount of mandatorily redeemable preferred interests of consolidated subsidiaries	313,095,000	315,885,000
Secured financing included in inventory and eliminated	$ 8,900,000	$ 15,700,000