Long-duration insurance contracts - Summary of gross premiums earned and net interest expense (Detail) - USD ($) $ in Millions	6 Months Ended
Jun. 30, 2025	Jun. 30, 2024
Periodic Payment Annuity [Member]
Liability for Future Policy Benefit, Activity [Line Items]
Net Interest Expense	$ 277	$ 273
Life and Health [Member]
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	1,961	1,870
Net Interest Expense	$ 67	$ 68

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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+ Details