Finance Receivables - Allowance for Loan Losses (Details) - Automobile Loan [Member] - Retail Finance Receivables [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	$ 765	$ 713	$ 638
Provision for loan losses	742	640	592
Charge-offs	(1,171)	(1,136)	(966)
Recoveries	552	542	469
Foreign currency translation	1	6	(20)
Balance at end of period	$ 889	$ 765	$ 713