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Financial Assets And Financial Liabilities (Netting of Financial Assets) (Details) - USD ($) $ in Millions | Dec. 31, 2017 | Dec. 31, 2016
--- | --- | ---
Securities, Segregated For Regulatory Purposes, Purchased Under Agreements To Resell [Abstract] |  |  |
Gross Amounts of Financial Assets Recognized | [1] | $ 9,166 | $ 10,995
Amounts Offset in the Consolidated Statement of Financial Condition | [2] |  |
Net Amounts Presented in the Consolidated Statement of Financial Condition |  | 9,166 | 10,995
Amounts Not Offset in the Consolidated Statement of Financial Condition: Cash or Financial Instruments |  | (9,166) | (10,995)
Net Amount |  |  |
Offsetting Securities Borrowed [Abstract] |  |  |
Gross Amounts of Financial Assets Recognized |  | 2,957 | 3,629
Amounts Offset in the Consolidated Statement of Financial Condition | [2] |  |
Net Amounts Presented in the Consolidated Statement of Financial Condition |  | 2,957 | 3,629
Amounts Not Offset in the Consolidated Statement of Financial Condition: Cash or Financial Instruments |  | (2,822) | (3,488)
Net Amount |  | 135 | 141
Offsetting Securities Purchased under Agreements to Resell [Abstract] |  |  |
Gross Amounts of Financial Assets Recognized |  | 2,035 | 111
Amounts Offset in the Consolidated Statement of Financial Condition | [2] |  |
Net Amounts Presented in the Consolidated Statement of Financial Condition |  | 2,035 | 111
Amounts Not Offset in the Consolidated Statement of Financial Condition: Cash or Financial Instruments |  | (2,035) | (111)
Net Amount |  |  |
Total [Abstract] |  |  |
Gross Amounts of Financial Assets Recognized |  | 15,247 | 16,585
Amounts Offset in the Consolidated Statement of Financial Condition | [2] |  |
Net Amounts Presented in the Consolidated Statement of Financial Condition |  | 15,247 | 16,585
Amounts Not Offset in the Consolidated Statement of Financial Condition: Cash or Financial Instruments |  | (14,474) | (15,825)
Net Amount |  | 773 | 760
Options [Member] |  |  |
Offsetting Financial Instruments Owned, At Fair Value [Abstract] |  |  |
Gross Amounts of Financial Assets Recognized |  | 1,052 | 1,804
Amounts Offset in the Consolidated Statement of Financial Condition | [2] |  |
Net Amounts Presented in the Consolidated Statement of Financial Condition |  | 1,052 | 1,804
Amounts Not Offset in the Consolidated Statement of Financial Condition: Cash or Financial Instruments |  | (451) | (1,230)
Net Amount |  | 601 | 574
Warrants And Discount Certificates [Member] |  |  |
Offsetting Financial Instruments Owned, At Fair Value [Abstract] |  |  |
Gross Amounts of Financial Assets Recognized |  | 5 | 43
Amounts Offset in the Consolidated Statement of Financial Condition | [2] |  |
Net Amounts Presented in the Consolidated Statement of Financial Condition |  | 5 | 43
Amounts Not Offset in the Consolidated Statement of Financial Condition: Cash or Financial Instruments |  |  | (1)
Net Amount |  | 5 | 42
Currency Forward Contracts [Member] |  |  |
Offsetting Financial Instruments Owned, At Fair Value [Abstract] |  |  |
Gross Amounts of Financial Assets Recognized |  | 32 | 3
Amounts Offset in the Consolidated Statement of Financial Condition | [2] |  |
Net Amounts Presented in the Consolidated Statement of Financial Condition |  | 32 | 3
Amounts Not Offset in the Consolidated Statement of Financial Condition: Cash or Financial Instruments |  |  |
Net Amount |  | $ 32 | $ 3
[1] | As of December 31, 2017 and December 31, 2016, the Company had $9.2 billion and $11.0 billion, respectively, of securities purchased under agreements to resell that were segregated to satisfy regulatory requirements. These securities are included in "Cash and securities - segregated for regulatory purposes" in the consolidated statements of financial condition.
[2] | The Company did not have any balances eligible for netting in accordance with ASC Topic 210-20 at December 31, 2017 and 2016.

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- Definition Amount of liability associated with funds outstanding loaned in the form of a security resale agreement between the entity and another party for the purchase and resale of identical or substantially the same securities at a date certain for a specified price. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=82849420&loc=SL20226003-175313 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312 + Details
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