Leased Vehicles - Minimum rental payments (Details) $ in Millions	Dec. 31, 2017 USD ($)
Operating Leases, Future Minimum Payments Receivable [Abstract]
2018	$ 6,848
2019	4,530
2020	1,759
2021	189
2022	12
Total	$ 13,338

Future minimum rental payments in aggregate as of the balance sheet date under operating leases.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84164653&loc=d3e41551-112718

+ Details

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Balance Type:	debit
Period Type:	instant

- References

No definition available.

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- Definition

Future rental payments receivable within one year of the balance sheet date under an operating lease.

+ References

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Data Type:	xbrli:monetaryItemType
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- Definition

Future rental payments receivable within the fifth year from the balance sheet date under an operating lease.

+ References

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- Definition

Future rental payments receivable within the fourth year from the balance sheet date under an operating lease.

+ References

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- Definition

Future rental payments receivable within the third year from the balance sheet date under an operating lease.

+ References

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- Definition

Future rental payments receivable within the second year from the balance sheet date under an operating lease.

+ References

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