Amount after accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business to produce goods and services and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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-Name Accounting Standards Codification
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
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Name:	us-gaap_PropertyPlantAndEquipmentNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Leases - Sale and Leased-backed asset and obligation (Details) - USD ($) $ in Millions	Sep. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
Property, plant and equipment - at cost
Finance lease asset	$ 8,891		$ 8,738
Finance lease liability	$ 134
Municipal securities
Property, plant and equipment - at cost
Finance lease liability		$ 9
Constructed machinery and equipment
Property, plant and equipment - at cost
Finance lease asset		$ 9