Derivative Financial Instruments (Details 2) (USD $) In Thousands	Aug. 31, 2011
Remaining contract maturity of fair value of over the counter derivative assets
OTC derivative assets having maturity period of 0 to 12 months	$ 359,800
OTC derivative assets having maturity period of 1 to 5 years	169,955
OTC derivative assets having maturity period of greater than 5 years	153,810
OTC derivative assets cross maturity netting	(25,578)
Total	657,987
Cross product counterparty netting	(17,588)
Total OTC derivative assets included in Financial instruments owned	640,399
Remaining contract maturity of fair value of Over The Counter derivative liabilities
OTC derivative liabilities having maturity period of 0 to 12 months	556,297
OTC derivative liabilities having maturity period of 1 to 5 years	243,704
OTC derivative liabilities having maturity period of greater than 5 years	167,734
OTC derivative liabilities cross maturity netting	(25,578)
Total	942,157
Cross product counterparty netting	(17,588)
Total OTC derivative liabilities included in Financial instruments sold, not yet purchased	924,569
Commodity swaps, options and forwards [Member]
Remaining contract maturity of fair value of over the counter derivative assets
OTC derivative assets having maturity period of 0 to 12 months	102,889
OTC derivative assets having maturity period of 1 to 5 years	11,396
OTC derivative assets having maturity period of greater than 5 years	0
OTC derivative assets cross maturity netting	(782)
Total	113,503
Commodity swaps, options and forwards [Member]
Remaining contract maturity of fair value of Over The Counter derivative liabilities
OTC derivative liabilities having maturity period of 0 to 12 months	258,951
OTC derivative liabilities having maturity period of 1 to 5 years	15,251
OTC derivative liabilities having maturity period of greater than 5 years	0
OTC derivative liabilities cross maturity netting	(782)
Total	273,420
Equity options [Member]
Remaining contract maturity of fair value of over the counter derivative assets
OTC derivative assets having maturity period of 0 to 12 months	17,992
OTC derivative assets having maturity period of 1 to 5 years	0
OTC derivative assets having maturity period of greater than 5 years	0
OTC derivative assets cross maturity netting	0
Total	17,992
Equity options [Member]
Remaining contract maturity of fair value of Over The Counter derivative liabilities
OTC derivative liabilities having maturity period of 0 to 12 months	11,079
OTC derivative liabilities having maturity period of 1 to 5 years	1,895
OTC derivative liabilities having maturity period of greater than 5 years	0
OTC derivative liabilities cross maturity netting	0
Total	12,974
Credit Default Swap [Member]
Remaining contract maturity of fair value of over the counter derivative assets
OTC derivative assets having maturity period of 0 to 12 months	468
OTC derivative assets having maturity period of 1 to 5 years	33,476
OTC derivative assets having maturity period of greater than 5 years	11,381
OTC derivative assets cross maturity netting	(263)
Total	45,062
Credit Default Swap [Member]
Remaining contract maturity of fair value of Over The Counter derivative liabilities
OTC derivative liabilities having maturity period of 0 to 12 months	1,001
OTC derivative liabilities having maturity period of 1 to 5 years	23,309
OTC derivative liabilities having maturity period of greater than 5 years	0
OTC derivative liabilities cross maturity netting	(263)
Total	24,047
Total return swaps [Member]
Remaining contract maturity of fair value of over the counter derivative assets
OTC derivative assets having maturity period of 0 to 12 months	518
OTC derivative assets having maturity period of 1 to 5 years	17
OTC derivative assets having maturity period of greater than 5 years	0
OTC derivative assets cross maturity netting	0
Total	535
Total return swaps [Member]
Remaining contract maturity of fair value of Over The Counter derivative liabilities
OTC derivative liabilities having maturity period of 0 to 12 months	0
OTC derivative liabilities having maturity period of 1 to 5 years	1,443
OTC derivative liabilities having maturity period of greater than 5 years	0
OTC derivative liabilities cross maturity netting	0
Total	1,443
Foreign currency forwards and swaps [Member]
Remaining contract maturity of fair value of over the counter derivative assets
OTC derivative assets having maturity period of 0 to 12 months	191,540
OTC derivative assets having maturity period of 1 to 5 years	36,420
OTC derivative assets having maturity period of greater than 5 years	3
OTC derivative assets cross maturity netting	(9,973)
Total	217,990
Foreign currency forwards and swaps [Member]
Remaining contract maturity of fair value of Over The Counter derivative liabilities
OTC derivative liabilities having maturity period of 0 to 12 months	238,109
OTC derivative liabilities having maturity period of 1 to 5 years	37,407
OTC derivative liabilities having maturity period of greater than 5 years	0
OTC derivative liabilities cross maturity netting	(9,973)
Total	265,543
Fixed income forwards [Member]
Remaining contract maturity of fair value of over the counter derivative assets
OTC derivative assets having maturity period of 0 to 12 months	92
OTC derivative assets having maturity period of 1 to 5 years	0
OTC derivative assets having maturity period of greater than 5 years	0
OTC derivative assets cross maturity netting	0
Total	92
Interest rate swaps and caps [Member]
Remaining contract maturity of fair value of over the counter derivative assets
OTC derivative assets having maturity period of 0 to 12 months	46,301
OTC derivative assets having maturity period of 1 to 5 years	88,646
OTC derivative assets having maturity period of greater than 5 years	142,426
OTC derivative assets cross maturity netting	(14,560)
Total	262,813
Interest rate swaps and caps [Member]
Remaining contract maturity of fair value of Over The Counter derivative liabilities
OTC derivative liabilities having maturity period of 0 to 12 months	47,157
OTC derivative liabilities having maturity period of 1 to 5 years	164,399
OTC derivative liabilities having maturity period of greater than 5 years	167,734
OTC derivative liabilities cross maturity netting	(14,560)
Total	$ 364,730