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Derivatives - Narrative (Details) € in Billions, £ in Billions |  | 1 Months Ended | 3 Months Ended | 12 Months Ended |
--- | --- | --- | --- | --- | ---
Sep. 20, 2018 GBP (£) | Mar. 31, 2019 USD ($) | Jan. 31, 2019 USD ($) | Jun. 30, 2019 USD ($) | Mar. 31, 2019 USD ($) | Mar. 31, 2018 USD ($) | Dec. 31, 2018 USD ($) | Mar. 31, 2019 EUR (€)
Derivative [Line Items] |  |  |  |  |  |  |  |
Total consideration |  |  |  |  | $ 177,000,000 | $ 36,000,000 |  |
Exchange rate | 0.0343 |  |  |  |  |  |  |
Foreign Exchange Forward |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |
Unrealized loss |  |  |  |  | 42,000,000 |  |  |
Treasury Lock |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |
Payments for derivative settlement |  |  | $ 122,000,000 |  | $ 6,000,000 |  |  |
Jardine Lloyd Thompson Group plc |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |
Total consideration | £ | £ 5.2 |  |  |  |  |  |  |
Jardine Lloyd Thompson Group plc | Treasury Lock |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |
Unrealized loss |  |  |  |  |  |  | $ 116,000,000 |
Derivative hedges, assets |  |  |  |  |  |  | $ 2,000,000,000 |
Senior Notes |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |
Proceeds from issuance of debt |  |  | $ 5,000,000,000 |  |  |  |  |
Senior Notes | Jardine Lloyd Thompson Group plc |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |
Proceeds from issuance of debt | € |  |  |  |  |  |  |  | € 1.1
Payments for derivative settlement |  | $ 7,300,000 |  |  |  |  |  |
Net investment hedge, threshold percentage of the equity balance |  |  |  |  | 80.00% |  |  |
Scenario, Forecast | Foreign Exchange Forward |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |
Unrealized loss |  |  |  | $ 12,000,000 |  |  |  |

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- Definition Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 30 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=109124213&loc=d3e6613-128477 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 30 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=109124213&loc=d3e6578-128477 + Details
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