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Long-duration insurance contracts - Summary of gross premiums earned and net interest expense (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024
Periodic Payment Annuity [Member]
Liability for Future Policy Benefit, Activity [Line Items]
Net Interest Expense	$ 417	$ 411
Life and Health [Member]
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	2,938	2,831
Net Interest Expense	$ 102	$ 100

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- Definition

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