Transactions with Related Parties (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Related Party Transaction
Dividend paid to Caterpillar									$ 400	$ 725	$ 275
Maximum borrowing capacity from Caterpillar, Variable lending agreements	$ 2,750								2,750
Maximum lending capacity to Caterpillar, Variable lending agreements	2,140								2,140
Amount available, Committed credit facility extended to Caterpillar	2,000								2,000
Payable to Caterpillar - borrowings	1,518				$ 1,638				1,518	1,638	1,637
Payable to Caterpillar - other	83				85				83	85	49
Notes receivable from Caterpillar	662				559				662	559	530
Other receivables from Caterpillar	153				74				153	74
Discounts earned on purchased receivables									375	253	207
Total revenues	699	$ 735	$ 723	$ 690	678	$ 673	$ 676	$ 662	2,847	2,689	2,595
Depreciation on equipment leased to others									819	810	841
Caterpillar
Related Party Transaction
Dividend paid to Caterpillar									400	725	275
Maximum borrowing capacity from Caterpillar, Variable lending agreements	2,750								2,750
Maximum lending capacity to Caterpillar, Variable lending agreements	2,140								2,140
Amount available, Committed credit facility extended to Caterpillar	2,000								2,000
Other receivables from Caterpillar	33				31				33	31	21
Interest expense, Caterpillar									35	21	15
Interest income on Notes Receivable with Caterpillar									30	74	30
Fees on committed credit facility extended to Caterpillar									40	40	40
Purchases of receivables from Caterpillar									42,961	34,667	28,631
Discounts earned on purchased receivables									375	253	207
Balance of purchased receivables	4,691				3,461				4,691	3,461	2,431
Marketing program payments received									335	277	273
Total portfolio, which includes finance receivables and equipment on operating lease, net of depreciation	56				17				56	17
Total revenues									9	4	8
Depreciation on equipment leased to others									5	3	7
Amount of our portfolio that is subject to guarantees by Caterpillar	$ 450				$ 481				450	481
Charges for employee medical plans and postretirement benefit plans administered by Caterpillar									34	31	29
Contributions to defined benefit plans									9	8	7
Stock based compensation expense									8	8	9
Operational and administrative support charges reimbursed to Caterpillar									35	30	28
Administrative support services to certain Caterpillar subsidiaries reimbursed by Caterpillar									$ 11	$ 9	$ 9