Accumulated Other Comprehensive Income Loss - AOCI Rollforward (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2022	Mar. 31, 2021
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	$ 17,843
Other comprehensive loss, net of tax	(1,871)	$ (906)
Ending balance	15,897	17,702
AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-sale, Parent [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	1,616	2,834
OCI before reclassifications	(2,469)	(1,166)
Amounts reclassified from AOCI	87	(4)
OCI, before tax	(2,382)	(1,170)
Other Comprehensive Income (Loss), Tax, Portion Attributable to Parent	500	245
Other comprehensive loss, net of tax	(1,882)	(925)
Ending balance	(266)	1,909
AOCI, Gain (Loss), Debt Securities, Available-for-sale, with Allowance for Credit Loss, Parent
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	(2)	(2)
OCI before reclassifications	0	0
Amounts reclassified from AOCI	0	0
OCI, before tax	0	0
Other Comprehensive Income (Loss), Tax, Portion Attributable to Parent	0	0
Other comprehensive loss, net of tax	0	0
Ending balance	(2)	(2)
Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	6	12
OCI before reclassifications	7	15
Amounts reclassified from AOCI	(8)	(9)
OCI, before tax	(1)	6
Other Comprehensive Income (Loss), Tax, Portion Attributable to Parent	0	(1)
Other comprehensive loss, net of tax	(1)	5
Ending balance	5	17
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	41	43
OCI before reclassifications	0	1
Amounts reclassified from AOCI	0	0
OCI, before tax	0	1
Other Comprehensive Income (Loss), Tax, Portion Attributable to Parent	0	0
Other comprehensive loss, net of tax	0	1
Ending balance	41	44
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	(1,489)	(1,717)
OCI before reclassifications	0	(1)
Amounts reclassified from AOCI	15	17
OCI, before tax	15	16
Other Comprehensive Income (Loss), Tax, Portion Attributable to Parent	(3)	(3)
Other comprehensive loss, net of tax	12	13
Ending balance	(1,477)	(1,704)
AOCI Attributable to Parent [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	172	1,170
OCI before reclassifications	(2,462)	(1,151)
Amounts reclassified from AOCI	94	4
OCI, before tax	(2,368)	(1,147)
Other Comprehensive Income (Loss), Tax, Portion Attributable to Parent	497	241
Other comprehensive loss, net of tax	(1,871)	(906)
Ending balance	$ (1,699)	$ 264

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount before tax and reclassification adjustments of other comprehensive income (loss) attributable to parent.

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Amount before tax of other comprehensive income (loss) attributable to parent entity.

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Amount of tax expense (benefit) allocated to other comprehensive income (loss) attributable to parent entity.

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Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.

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