Reflects the estimated amount of loss from the specified contingency as of the balance sheet date.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
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-Section 50
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
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-URI http://asc.fasb.org/extlink&oid=118943654&loc=d3e12021-110248

Name:	us-gaap_LossContingencyEstimateOfPossibleLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Claims, Lawsuits And Other Contingencies (Details) $ in Millions	Mar. 31, 2020 USD ($)	Mar. 31, 2020 GBP (£)	Feb. 28, 2019 USD ($)	Feb. 28, 2019 GBP (£)
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