Financial Services Finance Receivables - Aging (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016
Financing Receivables, Aging [Line Items]
Number Of Days After Which Finance Receivable Is Considered Past Due	31 days
Financing Receivable, Gross	$ 104,439	$ 96,674	$ 95,642
Consumer [Member]
Financing Receivables, Aging [Line Items]
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing	28	21
Financing Receivable, Recorded Investment, Past Due	870	947
Financing Receivable, Recorded Investment, Current	71,446	64,391
Financing Receivable, Gross	72,316	65,338	65,109
Consumer [Member] | Financing Receivables, 31 to 60 Days Past due [Member]
Financing Receivables, Aging [Line Items]
Financing Receivable, Recorded Investment, Past Due	682	760
Consumer [Member] | Financing Receivables, 61 to 90 Days Past due [Member]
Financing Receivables, Aging [Line Items]
Financing Receivable, Recorded Investment, Past Due	111	114
Consumer [Member] | Financing Receivables, 91 to 120 Days Past due [Member]
Financing Receivables, Aging [Line Items]
Financing Receivable, Recorded Investment, Past Due	40	34
Consumer [Member] | Financing Receivables, Greater than 120 Days Past due [Member]
Financing Receivables, Aging [Line Items]
Financing Receivable, Recorded Investment, Past Due	37	39
Non-consumer [Member]
Financing Receivables, Aging [Line Items]
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing	1	0
Financing Receivable, Recorded Investment, Past Due	135	107
Financing Receivable, Recorded Investment, Current	31,988	31,229
Financing Receivable, Gross	$ 32,123	$ 31,336	$ 30,533