Claims, Lawsuits And Other Contingencies (Details) numberOfCases in Thousands, $ in Millions	48 Months Ended
	Dec. 31, 2018 numberOfCases	Sep. 30, 2020 GBP (£)	Sep. 30, 2020 USD ($)	Feb. 28, 2019 GBP (£)	Feb. 28, 2019 USD ($)
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]
Individual cases analyzed | numberOfCases	14
Loss contingency accrual		£ 62,000,000	$ 79	£ 59,000,000	$ 77