Significant Accounting Policies - Deferred Acquisition Costs (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Deferred acquisition costs, beginning of the period	$ 1,747	$ 1,502
Capitalization	389	405
Amortization expense	(255)	(217)
Deferred acquisition costs, end of the period	$ 1,881	$ 1,690