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Leases - Narrative (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended |  |
--- | --- | --- | --- | ---
Sep. 30, 2019 | Sep. 30, 2019 | Mar. 31, 2019 | Dec. 31, 2018
Lessee, Lease, Description [Line Items] |  |  |  |
Percentage of lease obligations used for office space |  | 98.00% |  |
Lessee, operating lease, lease not yet commenced, amount | $ 71 | $ 71 |  |
Lessee, operating lease, lease not yet commenced, term (years) | 12 months | 12 months |  |
Operating lease, right-of-use asset | $ 1,957 | $ 1,957 |  | $ 0
Operating lease, liability | 2,298 | 2,298 |  |
Operating lease, impairment loss | $ 7 | $ 7 |  |
Minimum |  |  |  |
Lessee, Lease, Description [Line Items] |  |  |  |
Lessee, operating lease, term of contract (years) | 10 years | 10 years |  |
Maximum |  |  |  |
Lessee, Lease, Description [Line Items] |  |  |  |
Lessee, operating lease, term of contract (years) | 25 years | 25 years |  |
Jardine Lloyd Thompson Group plc |  |  |  |
Lessee, Lease, Description [Line Items] |  |  |  |
Operating lease, right-of-use asset |  |  | $ 400 |
Operating lease, liability |  |  | $ 400 |

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- Definition Term of lessee's operating lease not yet commenced, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=77888426&loc=SL77918673-209980 + Details
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- Definition Term of lessee's operating lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=77888426&loc=SL77918673-209980 + Details
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- Definition Amount of loss from impairment of right-of-use asset from operating lease. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 25 -Paragraph 6 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=77888369&loc=SL77918431-209957 + Details
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