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Claims, Lawsuits And Other Contingencies (Details) $ in Millions | Mar. 31, 2020 USD ($) | Mar. 31, 2020 GBP (£) | Feb. 28, 2019 USD ($) | Feb. 28, 2019 GBP (£)
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Loss Contingencies [Line Items] |  |  |  |
Loss contingency, estimate of possible loss | $ 91 | £ 73,000,000 |  |
Other Contingencies-Guarantees |  |  |  |
Loss Contingencies [Line Items] |  |  |  |
Amount reinsured by third party (up to) |  | £ 40,000,000 |  |
Jardine Lloyd Thompson Group plc |  |  |  |
Loss Contingencies [Line Items] |  |  |  |
Loss contingency accrual |  |  | $ 77 | £ 59,000,000

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