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Commitments, Contingencies and Guarantees (Narrative) (Details) - USD ($) $ in Millions | 2 Months Ended | 12 Months Ended
--- | --- | ---
Feb. 27, 2019 | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Commitment And Contingencies [Line Items] |  |  |  |
Rent expense |  | $ 15 | $ 15 | $ 16
Total future minimum annual lease commitments |  | $ 167 |  |
Subsequent Event [Member] |  |  |  |
Commitment And Contingencies [Line Items] |  |  |  |
Aggregate loss on securities | $ 47 |  |  |
Maximum aggregate loss, if securities' price falls to zero and no debts collected | $ 59 |  |  |

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- Definition Commitment And Contingencies [Line Items] + References No definition available. + Details
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- Definition Maximum Aggregate Loss, If Securities' Price Falls To Zero And No Debts Collected + References No definition available. + Details
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- Definition Amount of rent expense incurred for leased assets, including but not limited to, furniture and equipment, that is not directly or indirectly associated with the manufacture, sale or creation of a product or product line. + References No definition available. + Details
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- Definition Amount of required minimum rental payments for leases having an initial or remaining non-cancelable letter-terms in excess of one year. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 10 -Section 55 -Paragraph 40 -Subparagraph (Note 3) -URI http://asc.fasb.org/extlink&oid=82846649&loc=d3e38371-112697 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 20 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=77902758&loc=d3e41502-112717 + Details
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