Other Comprehensive Income (Loss) - Components of other comprehensive income (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Before tax amount:
Unrealized holding gains (losses) arising during period, before tax	$ (208)	$ (672)	$ (131)	$ (2,132)
Less reclassification of net realized gains included in net income, before tax	(104)	(47)	(368)	(234)
Foreign currency translation adjustments, before tax	(40)	(70)	(33)	(141)
Other comprehensive income (loss), before tax	(144)	(695)	204	(2,039)
Tax expense (benefit):
Unrealized holding gains (losses) arising during period, tax	(18)	(62)	(13)	(240)
Less reclassification of net realized gains included in net income, tax	(8)	(1)	(24)	(28)
Foreign currency translation adjustments, tax	0	0	0	0
Other comprehensive income (loss), tax	(10)	(61)	11	(212)
Net of tax amount:
Unrealized holding gains (losses) arising during period, net of tax	(190)	(610)	(118)	(1,892)
Less reclassification of net realized gains included in net income, net of tax	(96)	(46)	(344)	(206)
Foreign currency translation adjustments, net of tax	(40)	(70)	(33)	(141)
Net current period other comprehensive income (loss)	$ (134)	$ (634)	$ 193	$ (1,827)