Financial Services Finance Receivables - Impaired (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Financing Receivable Impaired [Line Items]
Number of Days Past Due After Which Consumer Receivables are Considered Impaired	120 days
Consumer [Member]
Financing Receivable Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	$ 379	$ 386
Impaired Financing Receivable Recorded Investment, Percentage of Receivable	0.50%	0.50%
Non-consumer [Member]
Financing Receivable Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	$ 165	$ 138
Impaired Financing Receivable Recorded Investment, Percentage of Receivable	0.50%	0.40%