Commitments and Contingencies (Detail) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended
	Nov. 16, 2023	Mar. 31, 2024
Other Commitments [Line Items]
Contractual commitments related to its limited partnership investments (up to)		$ 93.7
Contractual commitments period (not to exceed)		12 years
Commitment to fund loan and mortgage loans		$ 29.4
Argo Group International Holdings, Inc. | Common Stock | Brookfield Reinsurance
Other Commitments [Line Items]
Equity interests issued and issuable (in dollars per share)	$ 30.00