Parent and Guarantor Condensed Consolidating Financial Statements (Schedule of Condensed Consolidating Balance Sheet) (Details) - USD ($) $ in Millions	Jun. 30, 2019	Mar. 31, 2019	Jan. 01, 2019	Dec. 31, 2018	Jun. 30, 2018	Mar. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents, noninterest-bearing	$ 659			$ 810
Cash and cash equivalents, interest-bearing	2,904			3,727
Cash and cash equivalents	3,563			4,537	$ 3,924
Equity securities	591			773
Available-for-sale securities	28,688			25,303
Held-to-maturity securities	2,461			2,362
Loans held-for-sale, net	275			314
Finance receivables and loans, net	129,210			129,926	125,544
Intercompany loans to nonbank subsidiary	0			0
Allowance for loan losses	(1,282)			(1,242)
Total finance receivables and loans, net	127,928			128,684
Net Investment in Lease	8,407			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	2,460			2,326
Other assets	6,075			6,153
Assets	180,448			178,869	171,345
Deposit liabilities, noninterest-bearing	162			142
Deposit liabilities, interest-bearing	116,163			106,036
Deposit liabilities	116,325			106,178
Short-term borrowings	6,519			9,987
Long-term debt	37,466			44,193
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	744			523
Unearned insurance premiums and service revenue	3,171			3,044
Accrued Liabilities and Other Liabilities	1,907			1,676
Total liabilities	166,132			165,601
Equity	14,316	$ 13,699	$ 13,266	13,268	13,139	$ 13,082	$ 13,375	$ 13,494
Total liabilities and equity	180,448			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
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	(1,987)			(1,770)	(1,585)
Equity securities	0			0
Available-for-sale securities	0			0
Held-to-maturity securities	(14)			(20)
Loans held-for-sale, net	0			0
Finance receivables and loans, net	14			0
Intercompany loans to nonbank subsidiary	(765)			(1,279)
Allowance for loan losses	0			0
Total finance receivables and loans, net	(751)			(1,279)
Net Investment in Lease	0			0
Intercompany receivables from bank subsidiary	(105)			(158)
Intercompany receivables from nonbank subsidiary	(155)			(174)
Investment in bank subsidiaries	(33,730)			(32,426)
Investment in nonbank subsidiaries	(7,096)			(6,928)
Premiums receivable and other insurance assets	0			0
Other assets	(1,739)			(1,526)
Assets	(45,577)			(44,281)
Deposit liabilities, noninterest-bearing	0			0
Deposit liabilities, interest-bearing	0			0
Deposit liabilities	(1,242)			(1,249)
Short-term borrowings	0			0
Long-term debt	0			0
Intercompany debt payable to bank subsidiaries	(14)			(20)
Intercompany debt payable to nonbank subsidiaries	(1,510)			(1,800)
Intercompany payables to bank subsidiary	(51)			(45)
Intercompany payables to nonbank subsidiaries	(215)			(253)
Interest payable	0			0
Unearned insurance premiums and service revenue	0			0
Accrued Liabilities and Other Liabilities	(1,734)			(1,560)
Total liabilities	(4,766)			(4,927)
Equity	(40,811)			(39,354)
Total liabilities and equity	(45,577)			(44,281)
Consolidating adjustments | Affiliated entity
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents, interest-bearing	(1,987)			(1,770)
Deposit liabilities, interest-bearing	(1,242)			(1,249)
Parent
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents, noninterest-bearing	44			55
Cash and cash equivalents, interest-bearing	6			5
Cash and cash equivalents	1,292			1,309	1,071
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	2,292			2,349
Intercompany loans to nonbank subsidiary	663			882
Allowance for loan losses	(34)			(55)
Total finance receivables and loans, net	2,921			3,176
Net Investment in Lease	2			5
Intercompany receivables from bank subsidiary	105			158
Intercompany receivables from nonbank subsidiary	40			45
Investment in bank subsidiaries	16,865			16,213
Investment in nonbank subsidiaries	7,096			6,928
Premiums receivable and other insurance assets	0			0
Other assets	2,339			2,226
Assets	30,660			30,060
Deposit liabilities, noninterest-bearing	0			0
Deposit liabilities, interest-bearing	1			1
Deposit liabilities	1			1
Short-term borrowings	2,462			2,477
Long-term debt	12,447			12,774
Intercompany debt payable to bank subsidiaries	14			20
Intercompany debt payable to nonbank subsidiaries	847			918
Intercompany payables to bank subsidiary	51			45
Intercompany payables to nonbank subsidiaries	108			124
Interest payable	150			159
Unearned insurance premiums and service revenue	0			0
Accrued Liabilities and Other Liabilities	264			274
Total liabilities	16,344			16,792
Equity	14,316			13,268
Total liabilities and equity	30,660			30,060
Parent | Affiliated entity
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents, interest-bearing	1,242			1,249
Deposit liabilities, interest-bearing	0			0
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	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	16,865			16,213
Investment in nonbank subsidiaries	0			0
Premiums receivable and other insurance assets	0			0
Other assets	0			0
Assets	16,865			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
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 Liabilities and Other Liabilities	0			0
Total liabilities	0			0
Equity	16,865			16,213
Total liabilities and equity	16,865			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
Nonguarantors
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents, noninterest-bearing	615			755
Cash and cash equivalents, interest-bearing	2,898			3,722
Cash and cash equivalents	4,258			4,998	$ 4,438
Equity securities	591			773
Available-for-sale securities	28,688			25,303
Held-to-maturity securities	2,475			2,382
Loans held-for-sale, net	275			314
Finance receivables and loans, net	126,904			127,577
Intercompany loans to nonbank subsidiary	102			397
Allowance for loan losses	(1,248)			(1,187)
Total finance receivables and loans, net	125,758			126,787
Net Investment in Lease	8,405			8,412
Intercompany receivables from bank subsidiary	0			0
Intercompany receivables from nonbank subsidiary	115			129
Investment in bank subsidiaries	0			0
Investment in nonbank subsidiaries	0			0
Premiums receivable and other insurance assets	2,460			2,326
Other assets	5,475			5,453
Assets	178,500			176,877
Deposit liabilities, noninterest-bearing	162			142
Deposit liabilities, interest-bearing	116,162			106,035
Deposit liabilities	117,566			107,426
Short-term borrowings	4,057			7,510
Long-term debt	25,019			31,419
Intercompany debt payable to bank subsidiaries	0			0
Intercompany debt payable to nonbank subsidiaries	663			882
Intercompany payables to bank subsidiary	0			0
Intercompany payables to nonbank subsidiaries	107			129
Interest payable	594			364
Unearned insurance premiums and service revenue	3,171			3,044
Accrued Liabilities and Other Liabilities	3,377			2,962
Total liabilities	154,554			153,736
Equity	23,946			23,141
Total liabilities and equity	178,500			176,877
Nonguarantors | Affiliated entity
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents, interest-bearing	745			521
Deposit liabilities, interest-bearing	$ 1,242			$ 1,249