Leases (Property under Operating Leases) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Lessor, Lease, Description [Line Items]
Gross property under operating leases	$ 37,997	$ 35,072
Accumulated amortization of property under operating leases	10,028	9,755
Property Under Operating Leases
Lessor, Lease, Description [Line Items]
Gross property under operating leases	447	445
Accumulated amortization of property under operating leases	$ 197	$ 173

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 1
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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-Section S99
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Amount before accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 1
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-URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

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