Derivative Financial Instruments (Details 2) (USD $) In Thousands, unless otherwise specified	Feb. 29, 2012
Remaining contract maturity of fair value of over the counter derivative assets
OTC derivative assets having maturity period of 0 to 12 months	$ 253,832
OTC derivative assets having maturity period of 1 to 5 years	78,356
OTC derivative assets having maturity period of greater than 5 years	135,132
OTC derivative assets cross maturity netting	(45,607)
Total	421,713
Cross product counterparty netting	(18,033)
Total OTC derivative assets included in Financial instruments owned	403,680
Remaining contract maturity of fair value of Over The Counter derivative liabilities
OTC derivative liabilities having maturity period of 0 to 12 months	209,127
OTC derivative liabilities having maturity period of 1 to 5 years	142,256
OTC derivative liabilities having maturity period of greater than 5 years	165,339
OTC derivative liabilities cross maturity netting	(45,607)
Total	471,115
Cross product counterparty netting	(18,033)
Total OTC derivative liabilities included in Financial instruments sold, not yet purchased	453,082
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	63,984
OTC derivative liabilities having maturity period of 1 to 5 years	5,630
OTC derivative liabilities cross maturity netting	(524)
Total	69,090
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	307
OTC derivative liabilities having maturity period of 1 to 5 years	7,372
Total	7,679
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	386
OTC derivative liabilities having maturity period of 1 to 5 years	5,627
OTC derivative liabilities having maturity period of greater than 5 years	9,502
OTC derivative liabilities cross maturity netting	(386)
Total	15,129
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	571
Total	571
Foreign currency forwards, swaps and 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	114,715
OTC derivative liabilities having maturity period of 1 to 5 years	27,934
OTC derivative liabilities cross maturity netting	(480)
Total	142,169
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	29,164
OTC derivative liabilities having maturity period of 1 to 5 years	95,693
OTC derivative liabilities having maturity period of greater than 5 years	155,837
OTC derivative liabilities cross maturity netting	(44,217)
Total	236,477
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	66,715
OTC derivative assets having maturity period of 1 to 5 years	3,098
OTC derivative assets cross maturity netting	(524)
Total	69,289
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	1,357
Total	1,357
Credit default swap [Member]
Remaining contract maturity of fair value of over the counter derivative assets
OTC derivative assets having maturity period of 1 to 5 years	9,300
OTC derivative assets having maturity period of greater than 5 years	7,155
OTC derivative assets cross maturity netting	(386)
Total	16,069
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	473
OTC derivative assets having maturity period of greater than 5 years	152
Total	625
Foreign currency forwards, swaps and 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	168,188
OTC derivative assets having maturity period of 1 to 5 years	34,270
OTC derivative assets cross maturity netting	(480)
Total	201,978
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	2,261
Total	2,261
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	14,838
OTC derivative assets having maturity period of 1 to 5 years	31,688
OTC derivative assets having maturity period of greater than 5 years	127,825
OTC derivative assets cross maturity netting	(44,217)
Total	$ 130,134