Parent and Guarantor Condensed Consolidating Financial Statements (Schedule of Condensed Consolidating Balance Sheet) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents, noninterest-bearing	$ 810		$ 844
Cash and cash equivalents, interest-bearing	3,727		3,408
Cash and cash equivalents	4,537		4,252
Equity securities	773		518
Available-for-sale securities	25,303		22,303
Held-to-maturity securities	2,362		1,899
Loans held-for-sale, net	314		108
Finance receivables and loans, net	129,926		122,893
Intercompany loans to nonbank subsidiary	0		0
Allowance for loan losses	1,242		1,276	$ 1,144
Total finance receivables and loans, net	128,684		121,617
Investment in operating leases, net	8,417		8,741
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	2,326		2,047
Other assets	6,153		5,663
Assets	178,869		167,148	163,728
Deposit liabilities, noninterest-bearing	142		108
Deposit liabilities, interest-bearing	106,036		93,148
Deposit liabilities	106,178		93,256
Short-term borrowings	9,987		11,413
Long-term debt	44,193		44,226
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
Interest payable	523		375
Unearned insurance premiums and service revenue	3,044		2,604
Accrued expenses and other liabilities	1,676		1,780
Total liabilities	165,601		153,654
Equity	13,268	$ 13,375	13,494	$ 13,317	$ 13,439
Total liabilities and equity	178,869		167,148
Parent
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents, noninterest-bearing	55		74
Cash and cash equivalents, interest-bearing	5		5
Cash and cash equivalents	1,309		1,217
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	2,349		7,434
Intercompany loans to nonbank subsidiary	882		879
Allowance for loan losses	55		185
Total finance receivables and loans, net	3,176		8,128
Investment in operating leases, net	5		19
Intercompany receivables from bank subsidiary	158		80
Intercompany receivables from nonbank subsidiary	45		71
Investment in bank subsidiaries	16,213		16,962
Investment in nonbank subsidiaries	6,928		8,111
Premiums receivable and other insurance assets	0		0
Other assets	2,226		2,207
Assets	30,060		36,795
Deposit liabilities, noninterest-bearing	0		0
Deposit liabilities, interest-bearing	1		12
Deposit liabilities	1		12
Short-term borrowings	2,477		3,171
Long-term debt	12,774		17,966
Intercompany debt payable to bank subsidiaries	20		74
Intercompany debt payable to nonbank subsidiaries	918		1,103
Intercompany payables to bank subsidiary	45		4
Intercompany payables to nonbank subsidiaries	124		132
Interest payable	159		200
Unearned insurance premiums and service revenue	0		0
Accrued expenses and other liabilities	274		639
Total liabilities	16,792		23,301
Equity	13,268		13,494
Total liabilities and equity	30,060		36,795
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
Investment in operating leases, net	0		0
Intercompany receivables from bank subsidiary	0		0
Intercompany receivables from nonbank subsidiary	0		0
Investment in bank subsidiaries	16,213		16,962
Investment in nonbank subsidiaries	0		0
Premiums receivable and other insurance assets	0		0
Other assets	0		0
Assets	16,213		16,962
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
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
Interest payable	0		0
Unearned insurance premiums and service revenue	0		0
Accrued expenses and other liabilities	0		0
Total liabilities	0		0
Equity	16,213		16,962
Total liabilities and equity	16,213		16,962
Nonguarantors
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents, noninterest-bearing	755		770
Cash and cash equivalents, interest-bearing	3,722		3,403
Cash and cash equivalents	4,998		4,868
Equity securities	773		518
Available-for-sale securities	25,303		22,303
Held-to-maturity securities	2,382		1,973
Loans held-for-sale, net	314		108
Finance receivables and loans, net	127,577		115,459
Intercompany loans to nonbank subsidiary	397		408
Allowance for loan losses	1,187		1,091
Total finance receivables and loans, net	126,787		114,776
Investment in operating leases, net	8,412		8,722
Intercompany receivables from bank subsidiary	0		0
Intercompany receivables from nonbank subsidiary	129		77
Investment in bank subsidiaries	0		0
Investment in nonbank subsidiaries	0		0
Premiums receivable and other insurance assets	2,326		2,082
Other assets	5,453		5,105
Assets	176,877		160,532
Deposit liabilities, noninterest-bearing	142		108
Deposit liabilities, interest-bearing	106,035		93,136
Deposit liabilities	107,426		94,383
Short-term borrowings	7,510		8,242
Long-term debt	31,419		26,260
Intercompany debt payable to bank subsidiaries	0		0
Intercompany debt payable to nonbank subsidiaries	882		879
Intercompany payables to bank subsidiary	0		0
Intercompany payables to nonbank subsidiaries	129		127
Interest payable	364		175
Unearned insurance premiums and service revenue	3,044		2,604
Accrued expenses and other liabilities	2,962		2,790
Total liabilities	153,736		135,460
Equity	23,141		25,072
Total liabilities and equity	176,877		160,532
Affiliated entity
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents, interest-bearing	0		0
Deposit liabilities, interest-bearing	0		0
Affiliated entity | Parent
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents, interest-bearing	1,249		1,138
Deposit liabilities, interest-bearing	0		0
Affiliated entity | Guarantors
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents, interest-bearing	0		0
Deposit liabilities, interest-bearing	0		0
Affiliated entity | Nonguarantors
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents, interest-bearing	521		695
Deposit liabilities, interest-bearing	1,249		1,139
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	(1,770)		(1,833)
Equity securities	0		0
Available-for-sale securities	0		0
Held-to-maturity securities	(20)		(74)
Loans held-for-sale, net	0		0
Finance receivables and loans, net	0		0
Intercompany loans to nonbank subsidiary	(1,279)		(1,287)
Allowance for loan losses	0		0
Total finance receivables and loans, net	(1,279)		(1,287)
Investment in operating leases, net	0		0
Intercompany receivables from bank subsidiary	(158)		(80)
Intercompany receivables from nonbank subsidiary	(174)		(148)
Investment in bank subsidiaries	(32,426)		(33,924)
Investment in nonbank subsidiaries	(6,928)		(8,111)
Premiums receivable and other insurance assets	0		(35)
Other assets	(1,526)		(1,649)
Assets	(44,281)		(47,141)
Deposit liabilities, noninterest-bearing	0		0
Deposit liabilities, interest-bearing	0		0
Deposit liabilities	(1,249)		(1,139)
Short-term borrowings	0		0
Long-term debt	0		0
Intercompany debt payable to bank subsidiaries	(20)		(74)
Intercompany debt payable to nonbank subsidiaries	(1,800)		(1,982)
Intercompany payables to bank subsidiary	(45)		(4)
Intercompany payables to nonbank subsidiaries	(253)		(259)
Interest payable	0		0
Unearned insurance premiums and service revenue	0		0
Accrued expenses and other liabilities	(1,560)		(1,649)
Total liabilities	(4,927)		(5,107)
Equity	(39,354)		(42,034)
Total liabilities and equity	(44,281)		(47,141)
Consolidating adjustments | Affiliated entity
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents, interest-bearing	(1,770)		(1,833)
Deposit liabilities, interest-bearing	$ (1,249)		$ (1,139)