Allowance for Credit Losses on Reinsurance Recoverables (Detail) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Allowance for Credit Losses
Beginning balance	$ 7.9	$ 0.0
Provision for credit losses	(1.9)	3.5
Charge-offs	0.0	0.0
Recoveries	0.0	0.0
Ending balance	6.0	6.8
Accounting Standards Update 2016-13 \| Cumulative Effect, Period of Adoption, Adjusted Balance
Allowance for Credit Losses
Beginning balance	$ 0.0	$ 3.3

Amount of the write-down or write-off of a receivable from a reinsurer.

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- Definition

Amount of increase in allowance for credit loss on reinsurance recoverable, from recovery.

+ References

+ Details

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

+ Details

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- Definition

Amount of expense (reversal of expense) for expected credit loss on reinsurance recoverable.

+ References

+ Details

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- Definition

Amount of allowance for credit loss on reinsurance recoverable.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 13
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121599337&loc=SL82919249-210447

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 13
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=121599337&loc=SL82919249-210447

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=121599878&loc=SL82895884-210446

+ Details

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- Details

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