Significant Accounting Policies - Deferred Acquisition Costs (Details) - USD ($) $ in Millions	9 Months Ended
Sep. 30, 2024	Sep. 30, 2023
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Deferred acquisition costs, beginning of the period	$ 1,502	$ 1,219
Capitalizations	405	414
Amortization expense	(217)	(196)
Deferred acquisition costs, end of the period	$ 1,690	$ 1,437

Amount of amortization expense (reversal of expense) for deferred policy acquisition costs.

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Name:	us-gaap_DeferredPolicyAcquisitionCostAmortizationExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration