Accumulated Other Comprehensive Income Loss - AOCI Rollforward (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance			$ 16,270
OCI, net of tax	$ 1,436	$ 687	427	$ 1,381
Ending balance	17,072	15,292	17,072	15,292
AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-sale, Parent [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	627	703	1,684	24
OCI before reclassifications	1,469	703	454	1,399
Amounts reclassified from AOCI	(41)	(39)	(83)	(56)
OCI, net of tax	1,428	664	371	1,343
Ending balance	2,055	1,367	2,055	1,367
Accumulated Other-than-Temporary Impairment Attributable to Parent [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	(2)	(3)	(3)	(4)
OCI before reclassifications	0	0	1	1
Amounts reclassified from AOCI	0	0	0	0
OCI, net of tax	0	0	1	1
Ending balance	(2)	(3)	(2)	(3)
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	53	0	9	(5)
OCI before reclassifications	0	13	47	19
Amounts reclassified from AOCI	(5)	(2)	(8)	(3)
OCI, net of tax	(5)	11	39	16
Ending balance	48	11	48	11
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	26	31	34	30
OCI before reclassifications	1	3	(7)	4
Amounts reclassified from AOCI	0	0	0	0
OCI, net of tax	1	3	(7)	4
Ending balance	27	34	27	34
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	(1,661)	(1,616)	(1,672)	(1,624)
OCI before reclassifications	0	0	(1)	0
Amounts reclassified from AOCI	12	9	24	17
OCI, net of tax	12	9	23	17
Ending balance	(1,649)	(1,607)	(1,649)	(1,607)
AOCI Attributable to Parent [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	(957)	(885)	52	(1,579)
OCI before reclassifications	1,470	719	494	1,423
Amounts reclassified from AOCI	(34)	(32)	(67)	(42)
OCI, net of tax	1,436	687	427	1,381
Ending balance	$ 479	$ (198)	$ 479	$ (198)

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 after tax, before reclassification adjustments, of other comprehensive income (loss), attributable to parent.

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

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

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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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