Collateralized Transactions (Collateral Pledged) (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending arrangements	$ 2,531,504	$ 2,843,911
Repurchase agreements	17,839,459	19,829,249
Total	20,370,963	22,673,160
Cash
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending arrangements	0
Repurchase agreements	4,361
Total	4,361
Corporate equity securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending arrangements	2,214,433	2,353,798
Repurchase agreements	490,609	214,413
Total	2,705,042	2,568,211
Corporate debt securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending arrangements	315,718	470,908
Repurchase agreements	1,496,127	2,336,702
Total	1,811,845	2,807,610
Mortgage- and asset-backed securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending arrangements	0	0
Repurchase agreements	2,667,439	2,562,268
Total	2,667,439	2,562,268
U.S. government and federal agency securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending arrangements	1,353	19,205
Repurchase agreements	10,124,642	11,792,534
Total	10,125,995	11,811,739
Municipal securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending arrangements	0	0
Repurchase agreements	582,699	444,861
Total	582,699	444,861
Sovereign obligations
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending arrangements	0	0
Repurchase agreements	1,955,879	2,023,530
Total	1,955,879	2,023,530
Loans and other receivables
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending arrangements	0	0
Repurchase agreements	517,703	454,941
Total	$ 517,703	$ 454,941

Amount, before effects of master netting arrangements, of funds outstanding borrowed in the form of a financial asset repurchase agreement between the entity and another party for the sale and repurchase of identical or substantially the same financial asset at a date certain for a specified price. Includes repurchase-to-maturity transactions and liabilities not subject to a master netting arrangement.

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- Definition

Amount, before effects of master netting arrangements, of financial assets loaned to entities in exchange for collateral and funds outstanding borrowed in the form of a financial asset repurchase agreement between the entity and another party for the sale and repurchase of identical or substantially the same financial assets at a date certain for a specified price. Includes liabilities not subject to a master netting arrangement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 50
-Paragraph 7
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109249958&loc=SL34722452-111729

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 50
-Paragraph 7
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=109249958&loc=SL34722452-111729

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- Definition

Amount, before effects of master netting arrangements, of financial assets loaned to entities in exchange for collateral. Includes liabilities not subject to a master netting arrangement and financial assets transferred other than securities that qualify as secured borrowings.

+ References

+ Details

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- Definition

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+ References

No definition available.

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