Accumulated Other Comprehensive Income Loss - AOCI Rollforward (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	$ 15,327
Other comprehensive income (loss), net of tax	(148)	$ 587
Ending balance	15,468	14,340
AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-sale, Parent [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	(1,482)	(2,594)
OCI before reclassifications	(210)	715
Amounts reclassified from AOCI	7	27
OCI, before tax	(203)	742
Other Comprehensive Income (Loss), Tax, Portion Attributable to Parent	43	(156)
Other comprehensive income (loss), net of tax	(160)	586
Ending balance	(1,642)	(2,008)
AOCI, Gain (Loss), Debt Securities, Available-for-sale, with Allowance for Credit Loss, Parent
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	(8)	(7)
OCI before reclassifications	1	(8)
Amounts reclassified from AOCI	0	0
OCI, before tax	1	(8)
Other Comprehensive Income (Loss), Tax, Portion Attributable to Parent	0	2
Other comprehensive income (loss), net of tax	1	(6)
Ending balance	(7)	(13)
Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	21	40
OCI before reclassifications	0	7
Amounts reclassified from AOCI	0	3
OCI, before tax	0	10
Other Comprehensive Income (Loss), Tax, Portion Attributable to Parent	0	(2)
Other comprehensive income (loss), net of tax	0	8
Ending balance	21	48
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	37	31
OCI before reclassifications	(1)	3
Amounts reclassified from AOCI	0	0
OCI, before tax	(1)	3
Other Comprehensive Income (Loss), Tax, Portion Attributable to Parent	0	(1)
Other comprehensive income (loss), net of tax	(1)	2
Ending balance	36	33
AOCI, Liability for Future Policy Benefit, Parent
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	25	35
OCI before reclassifications	6	(10)
Amounts reclassified from AOCI	0	0
OCI, before tax	6	(10)
Other Comprehensive Income (Loss), Tax, Portion Attributable to Parent	(1)	2
Other comprehensive income (loss), net of tax	5	(8)
Ending balance	30	27
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	(1,442)	(1,346)
OCI before reclassifications	2	0
Amounts reclassified from AOCI	7	6
OCI, before tax	9	6
Other Comprehensive Income (Loss), Tax, Portion Attributable to Parent	(2)	(1)
Other comprehensive income (loss), net of tax	7	5
Ending balance	(1,435)	(1,341)
AOCI Attributable to Parent [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	(2,849)	(3,841)
OCI before reclassifications	(202)	707
Amounts reclassified from AOCI	14	36
OCI, before tax	(188)	743
Other Comprehensive Income (Loss), Tax, Portion Attributable to Parent	40	(156)
Other comprehensive income (loss), net of tax	(148)	587
Ending balance	$ (2,997)	$ (3,254)