Collateralized Transactions - Collateral Pledged (Details) $ in Thousands	Aug. 31, 2015 USD ($)
Transfer Of Certain Financial Assets Accounted For As Secured Borrowings [Line Items]
Securities Lending Arrangements	$ 3,645,195
Repurchase Agreements	19,478,562
Total	23,123,757
Corporate equity securities [Member]
Transfer Of Certain Financial Assets Accounted For As Secured Borrowings [Line Items]
Securities Lending Arrangements	2,506,969
Repurchase Agreements	347,844
Total	2,854,813
Corporate debt securities [Member]
Transfer Of Certain Financial Assets Accounted For As Secured Borrowings [Line Items]
Securities Lending Arrangements	1,109,775
Repurchase Agreements	1,959,647
Total	3,069,422
Mortgage- and asset-backed securities [Member]
Transfer Of Certain Financial Assets Accounted For As Secured Borrowings [Line Items]
Securities Lending Arrangements	0
Repurchase Agreements	5,044,406
Total	5,044,406
U.S. government and federal agency securities [Member]
Transfer Of Certain Financial Assets Accounted For As Secured Borrowings [Line Items]
Securities Lending Arrangements	28,451
Repurchase Agreements	9,412,058
Total	9,440,509
Municipal securities [Member]
Transfer Of Certain Financial Assets Accounted For As Secured Borrowings [Line Items]
Securities Lending Arrangements	0
Repurchase Agreements	492,599
Total	492,599
Sovereign obligations [Member]
Transfer Of Certain Financial Assets Accounted For As Secured Borrowings [Line Items]
Securities Lending Arrangements	0
Repurchase Agreements	1,604,147
Total	1,604,147
Loans and other receivables [Member]
Transfer Of Certain Financial Assets Accounted For As Secured Borrowings [Line Items]
Securities Lending Arrangements	0
Repurchase Agreements	617,861
Total	$ 617,861