Leases - Components of balance sheet (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Operating lease right-of-use assets	$ 985	$ 0
Current portion of operating lease liabilities	208	0
Operating lease liabilities	762	$ 0
Other Assets [Member]
Finance Lease, Right-of-Use Asset	136
Other Current Liabilities [Member]
Finance Lease, Liability, Current	18
Other Liabilities [Member]
Finance Lease, Liability, Noncurrent	$ 128

Present value of lessee's discounted obligation for lease payments from finance lease, classified as current.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 45
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=77888419&loc=SL77918627-209977

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- Definition

Present value of lessee's discounted obligation for lease payments from finance lease, classified as noncurrent.

+ References

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- Definition

Amount of lessee's right to use underlying asset under finance lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 45
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=77888419&loc=SL77918627-209977

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- Definition

Present value of lessee's discounted obligation for lease payments from operating lease, classified as current.

+ References

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- Definition

Amount of lessee's right to use underlying asset under operating lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 45
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=77888419&loc=SL77918627-209977

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