Finance Receivables - Aging Analysis (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Finance Receivables Aging Analysis [Abstract]
Financing Receivable, Gross	$ 106,375	$ 114,830
Consumer Segment [Member]
Finance Receivables Aging Analysis [Abstract]
Financing Receivable, Gross	78,170
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	845
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	2,599
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	6,790
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	13,939
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	21,074
Financing Receivable, Year One, Originated, Current Fiscal Year	32,923
Non-Consumer Segment [Member]
Finance Receivables Aging Analysis [Abstract]
Financing Receivable, Gross	28,205	$ 40,855
Financing Receivable, Revolving	24,996
Non-Consumer Segment [Member] | Dealer Loan
Finance Receivables Aging Analysis [Abstract]
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	552
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	149
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	124
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	242
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	78
Financing Receivable, Year One, Originated, Current Fiscal Year	376
Non-Consumer Segment [Member] | Group I [Member]
Finance Receivables Aging Analysis [Abstract]
Financing Receivable, Gross	20,017
Financing Receivable, Revolving	18,769
Non-Consumer Segment [Member] | Group I [Member] | Dealer Loan
Finance Receivables Aging Analysis [Abstract]
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	503
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	129
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	110
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	188
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	70
Financing Receivable, Year One, Originated, Current Fiscal Year	248
Non-Consumer Segment [Member] | Group II [Member]
Finance Receivables Aging Analysis [Abstract]
Financing Receivable, Gross	4,874
Financing Receivable, Revolving	4,680
Non-Consumer Segment [Member] | Group II [Member] | Dealer Loan
Finance Receivables Aging Analysis [Abstract]
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	38
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	20
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	11
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	35
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	3
Financing Receivable, Year One, Originated, Current Fiscal Year	87
Non-Consumer Segment [Member] | Group III [Member]
Finance Receivables Aging Analysis [Abstract]
Financing Receivable, Gross	1,533
Financing Receivable, Revolving	1,464
Non-Consumer Segment [Member] | Group III [Member] | Dealer Loan
Finance Receivables Aging Analysis [Abstract]
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	9
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	3
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	19
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	3
Financing Receivable, Year One, Originated, Current Fiscal Year	35
Non-Consumer Segment [Member] | Group IV [Member]
Finance Receivables Aging Analysis [Abstract]
Financing Receivable, Gross	93
Financing Receivable, Revolving	83
Non-Consumer Segment [Member] | Group IV [Member] | Dealer Loan
Finance Receivables Aging Analysis [Abstract]
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	2
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	2
Financing Receivable, Year One, Originated, Current Fiscal Year	6
Financial Asset, 1 to 29 Days Past Due [Member] | Consumer Segment [Member]
Finance Receivables Aging Analysis [Abstract]
Financing Receivable, Gross	77,285
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	782
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	2,519
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	6,656
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	13,725
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	20,856
Financing Receivable, Year One, Originated, Current Fiscal Year	32,747
31-60 Days Past Due [Member] | Consumer Segment [Member]
Finance Receivables Aging Analysis [Abstract]
Financing Receivable, Gross	681
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	45
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	62
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	103
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	162
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	166
Financing Receivable, Year One, Originated, Current Fiscal Year	143
Financing Receivables, 61-120 Days past due [Member] | Consumer Segment [Member]
Finance Receivables Aging Analysis [Abstract]
Financing Receivable, Gross	163
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	7
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	12
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	24
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	44
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	45
Financing Receivable, Year One, Originated, Current Fiscal Year	31
Greater Than 120 Days Past Due [Member] | Consumer Segment [Member]
Finance Receivables Aging Analysis [Abstract]
Financing Receivable, Gross	41
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	11
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	6
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	7
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	8
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	7
Financing Receivable, Year One, Originated, Current Fiscal Year	2
Total past due [Member] | Consumer Segment [Member]
Finance Receivables Aging Analysis [Abstract]
Financing Receivable, Gross	885
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	63
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	80
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	134
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	214
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	218
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 176