Revenue Recognition - Future Minimum Payments Receivable (Details) $ in Millions	12 Months Ended
Dec. 31, 2020 USD ($) term
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Total lease payments	$ 731
Less than 1 year	56
More than 5 years	$ 451
Transportation Services Operating Leases Five Year Terms
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Initial term	10 years
Number of additional terms \| term	2
Additional term	5 years
Transportation Services Operating Leases Amended
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Additional term	14 months
Transportation Services Operating Leases One Year Terms
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Initial term	10 years
Number of additional terms \| term	10
Additional term	1 year
Transportation Services Operating Leases
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Initial term	10 years
Lease And Non-Lease Service Components
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Total lease payments	$ 735
Less than 1 year	111
Years 2 to 3	220
Years 4 to 5	220
More than 5 years	$ 184

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No definition available.

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Amount of lease payments to be received by lessor for operating lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 30
-Section 50
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=121576215&loc=SL77919396-209981

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Amount of lease payment to be received by lessor for operating lease after fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Term of lessor's operating lease renewal, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 30
-Section 50
-Paragraph 3
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