Parent and Guarantor Condensed Consolidating Financial Statements (Schedule of Condensed Consolidating Balance Sheet) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017	Jan. 01, 2017
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents, noninterest-bearing	$ 619		$ 810
Cash and cash equivalents, interest-bearing	2,936		3,727
Cash and cash equivalents	3,555		4,537
Equity securities	616		773
Available-for-sale securities	30,284		25,303
Held-to-maturity securities	1,568		2,362
Loans held-for-sale, net	158		314
Finance receivables and loans, net	128,231		129,926
Intercompany loans to nonbank subsidiary	0		0
Allowance for loan losses	(1,263)		(1,242)
Total finance receivables and loans, net	126,968		128,684
Net Investment in Lease	8,864		8,417
Intercompany receivables from bank subsidiary	0		0
Intercompany receivables from nonbank subsidiary	0		0
Investment in bank subsidiaries	0		0
Investment in nonbank subsidiaries	0		0
Premiums receivable and other insurance assets	2,558		2,326
Other assets	6,073		6,153
Assets	180,644		178,869		$ 167,148
Deposit liabilities, noninterest-bearing	119		142
Deposit liabilities, interest-bearing	120,633		106,036
Deposit liabilities	120,752		106,178
Short-term borrowings	5,531		9,987
Long-term debt	34,027		44,193
Interest payable	641		523
Unearned insurance premiums and service revenue	3,305		3,044
Accrued expenses and other liabilities	1,972		1,676
Total liabilities	166,228		165,601
Equity	14,416	$ 13,266	13,268	$ 13,375	$ 13,494	$ 13,317
Total liabilities and equity	180,644		178,869
Affiliated entity
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents, interest-bearing	0		0
Deposit liabilities, interest-bearing	0		0
Intercompany debt payable to bank subsidiaries	0		0
Intercompany debt payable to nonbank subsidiaries	0		0
Intercompany payables to bank subsidiary	0		0
Intercompany payables to nonbank subsidiaries	0		0
Consolidating adjustments
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents, noninterest-bearing	0		0
Cash and cash equivalents, interest-bearing	0		0
Cash and cash equivalents	(3,138)		(1,770)
Equity securities	0		0
Available-for-sale securities	0		0
Held-to-maturity securities	(10)		(20)
Loans held-for-sale, net	0		0
Finance receivables and loans, net	10		0
Intercompany loans to nonbank subsidiary	(271)		(1,279)
Allowance for loan losses	0		0
Total finance receivables and loans, net	(261)		(1,279)
Net Investment in Lease	0		0
Intercompany receivables from bank subsidiary	(94)		(158)
Intercompany receivables from nonbank subsidiary	(127)		(174)
Investment in bank subsidiaries	(33,908)		(32,426)
Investment in nonbank subsidiaries	(6,535)		(6,928)
Premiums receivable and other insurance assets	0		0
Other assets	(1,810)		(1,526)
Assets	(45,883)		(44,281)
Deposit liabilities, noninterest-bearing	0		0
Deposit liabilities, interest-bearing	0		0
Deposit liabilities	(2,051)		(1,249)
Short-term borrowings	0		0
Long-term debt	0		0
Interest payable	0		0
Unearned insurance premiums and service revenue	0		0
Accrued expenses and other liabilities	(1,782)		(1,560)
Total liabilities	(5,450)		(4,927)
Equity	(40,433)		(39,354)
Total liabilities and equity	(45,883)		(44,281)
Consolidating adjustments | Affiliated entity
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents, interest-bearing	(3,138)		(1,770)
Deposit liabilities, interest-bearing	(2,051)		(1,249)
Intercompany debt payable to bank subsidiaries	(10)		(20)
Intercompany debt payable to nonbank subsidiaries	(1,358)		(1,800)
Intercompany payables to bank subsidiary	(18)		(45)
Intercompany payables to nonbank subsidiaries	(231)		(253)
Parent
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents, noninterest-bearing	49		55
Cash and cash equivalents, interest-bearing	5		5
Cash and cash equivalents	2,105		1,309
Equity securities	0		0
Available-for-sale securities	0		0
Held-to-maturity securities	0		0
Loans held-for-sale, net	0		0
Finance receivables and loans, net	2,167		2,349
Intercompany loans to nonbank subsidiary	161		882
Allowance for loan losses	(22)		(55)
Total finance receivables and loans, net	2,306		3,176
Net Investment in Lease	1		5
Intercompany receivables from bank subsidiary	94		158
Intercompany receivables from nonbank subsidiary	50		45
Investment in bank subsidiaries	16,954		16,213
Investment in nonbank subsidiaries	6,535		6,928
Premiums receivable and other insurance assets	0		0
Other assets	2,193		2,226
Assets	30,238		30,060
Deposit liabilities, noninterest-bearing	0		0
Deposit liabilities, interest-bearing	1		1
Deposit liabilities	1		1
Short-term borrowings	2,581		2,477
Long-term debt	11,389		12,774
Interest payable	145		159
Unearned insurance premiums and service revenue	0		0
Accrued expenses and other liabilities	383		274
Total liabilities	15,822		16,792
Equity	14,416		13,268
Total liabilities and equity	30,238		30,060
Parent | Affiliated entity
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents, interest-bearing	2,051		1,249
Deposit liabilities, interest-bearing	0		0
Intercompany debt payable to bank subsidiaries	10		20
Intercompany debt payable to nonbank subsidiaries	1,197		918
Intercompany payables to bank subsidiary	18		45
Intercompany payables to nonbank subsidiaries	98		124
Guarantors
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents, noninterest-bearing	0		0
Cash and cash equivalents, interest-bearing	0		0
Cash and cash equivalents	0		0
Equity securities	0		0
Available-for-sale securities	0		0
Held-to-maturity securities	0		0
Loans held-for-sale, net	0		0
Finance receivables and loans, net	0		0
Intercompany loans to nonbank subsidiary	0		0
Allowance for loan losses	0		0
Total finance receivables and loans, net	0		0
Net Investment in Lease	0		0
Intercompany receivables from bank subsidiary	0		0
Intercompany receivables from nonbank subsidiary	0		0
Investment in bank subsidiaries	16,954		16,213
Investment in nonbank subsidiaries	0		0
Premiums receivable and other insurance assets	0		0
Other assets	0		0
Assets	16,954		16,213
Deposit liabilities, noninterest-bearing	0		0
Deposit liabilities, interest-bearing	0		0
Deposit liabilities	0		0
Short-term borrowings	0		0
Long-term debt	0		0
Interest payable	0		0
Unearned insurance premiums and service revenue	0		0
Accrued expenses and other liabilities	0		0
Total liabilities	0		0
Equity	16,954		16,213
Total liabilities and equity	16,954		16,213
Guarantors | Affiliated entity
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents, interest-bearing	0		0
Deposit liabilities, interest-bearing	0		0
Intercompany debt payable to bank subsidiaries	0		0
Intercompany debt payable to nonbank subsidiaries	0		0
Intercompany payables to bank subsidiary	0		0
Intercompany payables to nonbank subsidiaries	0		0
Nonguarantors
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents, noninterest-bearing	570		755
Cash and cash equivalents, interest-bearing	2,931		3,722
Cash and cash equivalents	4,588		4,998
Equity securities	616		773
Available-for-sale securities	30,284		25,303
Held-to-maturity securities	1,578		2,382
Loans held-for-sale, net	158		314
Finance receivables and loans, net	126,054		127,577
Intercompany loans to nonbank subsidiary	110		397
Allowance for loan losses	(1,241)		(1,187)
Total finance receivables and loans, net	124,923		126,787
Net Investment in Lease	8,863		8,412
Intercompany receivables from bank subsidiary	0		0
Intercompany receivables from nonbank subsidiary	77		129
Investment in bank subsidiaries	0		0
Investment in nonbank subsidiaries	0		0
Premiums receivable and other insurance assets	2,558		2,326
Other assets	5,690		5,453
Assets	179,335		176,877
Deposit liabilities, noninterest-bearing	119		142
Deposit liabilities, interest-bearing	120,632		106,035
Deposit liabilities	122,802		107,426
Short-term borrowings	2,950		7,510
Long-term debt	22,638		31,419
Interest payable	496		364
Unearned insurance premiums and service revenue	3,305		3,044
Accrued expenses and other liabilities	3,371		2,962
Total liabilities	155,856		153,736
Equity	23,479		23,141
Total liabilities and equity	179,335		176,877
Nonguarantors | Affiliated entity
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents, interest-bearing	1,087		521
Deposit liabilities, interest-bearing	2,051		1,249
Intercompany debt payable to bank subsidiaries	0		0
Intercompany debt payable to nonbank subsidiaries	161		882
Intercompany payables to bank subsidiary	0		0
Intercompany payables to nonbank subsidiaries	$ 133		$ 129