|**Other Assets (Tables)**                           | 12 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                           
|--------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
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|**Other Assets [Abstract]**                         |                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|Schedule of other assets                            | The components of other assets as of December 31, were as follows:(Millions of dollars)20182017Customer and other miscellaneous receivables$480$457Collateral held for resale, at net realizable value316432Deferred and refundable income taxes191174Property and equipment, net12862Other(1)15374Total other assets$1,268$1,199(1)Includes$33 millionand$31 millionof other receivables from Caterpillar as of December 31, 2018 and 2017, respectively.
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|(Millions of dollars)                               |                                                                                                                                                                                                                                                                                                                                                                                                                                                           
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|Customer and other miscellaneous receivables        |                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|Collateral held for resale, at net realizable value |                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|Deferred and refundable income taxes                |                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|Property and equipment, net                         |                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|Other(1)                                            |                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|Total other assets                                  |                                                                                                                                                                                                                                                                                                                                                                                                                                                           
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