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Lease Commitments - Assets and Liabilities of Lessee (Details) - USD ($) $ in Millions | Dec. 31, 2020 | Dec. 31, 2019
--- | --- | ---
Assets |  |
Operating lease assets | $ 911 | $ 929
Finance lease assets | $ 89 | $ 100
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List] | us-gaap:OtherAssetsNoncurrent | us-gaap:OtherAssetsNoncurrent
Total lease assets | $ 1,000 | $ 1,029
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List] | us-gaap:OtherLiabilitiesCurrent | us-gaap:OtherLiabilitiesCurrent
Current lease liabilities |  |
Operating | $ 204 | $ 186
Finance | $ 30 | $ 24
Finance Lease, Liability, Current, Statement of Financial Position [Extensible List] | us-gaap:OtherLiabilitiesCurrent | us-gaap:OtherLiabilitiesCurrent
Non-current lease liabilities |  |
Operating | $ 897 | $ 944
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List] | us-gaap:OtherLiabilitiesNoncurrent | us-gaap:OtherLiabilitiesNoncurrent
Finance | $ 65 | $ 76
Total lease liabilities | $ 1,196 | $ 1,230

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- Definition Present value of lessee's discounted obligation for lease payments from finance lease, classified as current. + 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 (b) -URI http://asc.fasb.org/extlink&oid=121603541&loc=SL77918627-209977 + Details
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