Parent and Guarantor Condensed Consolidating Financial Statements (Schedule of Condensed Consolidating Balance Sheet) (Details) - USD ($) $ in Millions	Sep. 30, 2019	Jun. 30, 2019	Jan. 01, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents, noninterest-bearing	$ 723			$ 810
Cash and cash equivalents, interest-bearing	2,894			3,727
Cash and cash equivalents	3,617			4,537	$ 3,772
Equity securities	570			773
Available-for-sale securities	29,384			25,303
Held-to-maturity securities	2,618			2,362
Loans held-for-sale, net	1,000			314
Finance receivables and loans, net	128,609			129,926	126,605
Intercompany loans to nonbank subsidiary	0			0
Allowance for loan losses	(1,277)			(1,242)
Total finance receivables and loans, net	127,332			128,684
Net Investment in Lease	8,653			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	2,521			2,326
Other assets	5,790			6,153
Assets	181,485			178,869	173,101
Deposit liabilities, noninterest-bearing	156			142
Deposit liabilities, interest-bearing	119,074			106,036
Deposit liabilities	119,230			106,178
Short-term borrowings	5,335			9,987
Long-term debt	35,730			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	894			523
Unearned insurance premiums and service revenue	3,246			3,044
Accrued expenses and other liabilities	2,600			1,676
Total liabilities	167,035			165,601
Equity	14,450	$ 14,316	$ 13,266	13,268	13,085	$ 13,139	$ 13,375	$ 13,494
Total liabilities and equity	181,485			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	(3,048)			(1,770)	(1,482)
Equity securities	0			0
Available-for-sale securities	0			0
Held-to-maturity securities	(12)			(20)
Loans held-for-sale, net	0			0
Finance receivables and loans, net	12			0
Intercompany loans to nonbank subsidiary	(216)			(1,279)
Allowance for loan losses	0			0
Total finance receivables and loans, net	(204)			(1,279)
Net Investment in Lease	0			0
Intercompany receivables from bank subsidiary	(255)			(158)
Intercompany receivables from nonbank subsidiary	(150)			(174)
Investment in bank subsidiaries	(33,962)			(32,426)
Investment in nonbank subsidiaries	(7,010)			(6,928)
Premiums receivable and other insurance assets	0			0
Other assets	(1,608)			(1,526)
Assets	(46,249)			(44,281)
Deposit liabilities, noninterest-bearing	0			0
Deposit liabilities, interest-bearing	0			0
Deposit liabilities	(2,004)			(1,249)
Short-term borrowings	0			0
Long-term debt	0			0
Intercompany debt payable to bank subsidiaries	(12)			(20)
Intercompany debt payable to nonbank subsidiaries	(1,260)			(1,800)
Intercompany payables to bank subsidiary	(36)			(45)
Intercompany payables to nonbank subsidiaries	(386)			(253)
Interest payable	0			0
Unearned insurance premiums and service revenue	0			0
Accrued expenses and other liabilities	(1,591)			(1,560)
Total liabilities	(5,289)			(4,927)
Equity	(40,960)			(39,354)
Total liabilities and equity	(46,249)			(44,281)
Consolidating adjustments | Affiliated entity
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents, interest-bearing	(3,048)			(1,770)
Deposit liabilities, interest-bearing	(2,004)			(1,249)
Parent
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents, noninterest-bearing	51			55
Cash and cash equivalents, interest-bearing	12			5
Cash and cash equivalents	2,067			1,309	968
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	2,383			2,349
Intercompany loans to nonbank subsidiary	118			882
Allowance for loan losses	(31)			(55)
Total finance receivables and loans, net	2,470			3,176
Net Investment in Lease	1			5
Intercompany receivables from bank subsidiary	255			158
Intercompany receivables from nonbank subsidiary	50			45
Investment in bank subsidiaries	16,981			16,213
Investment in nonbank subsidiaries	7,010			6,928
Premiums receivable and other insurance assets	0			0
Other assets	2,044			2,226
Assets	30,878			30,060
Deposit liabilities, noninterest-bearing	0			0
Deposit liabilities, interest-bearing	1			1
Deposit liabilities	1			1
Short-term borrowings	2,501			2,477
Long-term debt	12,319			12,774
Intercompany debt payable to bank subsidiaries	12			20
Intercompany debt payable to nonbank subsidiaries	1,142			918
Intercompany payables to bank subsidiary	36			45
Intercompany payables to nonbank subsidiaries	109			124
Interest payable	182			159
Unearned insurance premiums and service revenue	0			0
Accrued expenses and other liabilities	126			274
Total liabilities	16,428			16,792
Equity	14,450			13,268
Total liabilities and equity	30,878			30,060
Parent | Affiliated entity
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents, interest-bearing	2,004			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	16,981			16,213
Investment in nonbank subsidiaries	0			0
Premiums receivable and other insurance assets	0			0
Other assets	0			0
Assets	16,981			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 expenses and other liabilities	0			0
Total liabilities	0			0
Equity	16,981			16,213
Total liabilities and equity	16,981			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	672			755
Cash and cash equivalents, interest-bearing	2,882			3,722
Cash and cash equivalents	4,598			4,998	$ 4,286
Equity securities	570			773
Available-for-sale securities	29,384			25,303
Held-to-maturity securities	2,630			2,382
Loans held-for-sale, net	1,000			314
Finance receivables and loans, net	126,214			127,577
Intercompany loans to nonbank subsidiary	98			397
Allowance for loan losses	(1,246)			(1,187)
Total finance receivables and loans, net	125,066			126,787
Net Investment in Lease	8,652			8,412
Intercompany receivables from bank subsidiary	0			0
Intercompany receivables from nonbank subsidiary	100			129
Investment in bank subsidiaries	0			0
Investment in nonbank subsidiaries	0			0
Premiums receivable and other insurance assets	2,521			2,326
Other assets	5,354			5,453
Assets	179,875			176,877
Deposit liabilities, noninterest-bearing	156			142
Deposit liabilities, interest-bearing	119,073			106,035
Deposit liabilities	121,233			107,426
Short-term borrowings	2,834			7,510
Long-term debt	23,411			31,419
Intercompany debt payable to bank subsidiaries	0			0
Intercompany debt payable to nonbank subsidiaries	118			882
Intercompany payables to bank subsidiary	0			0
Intercompany payables to nonbank subsidiaries	277			129
Interest payable	712			364
Unearned insurance premiums and service revenue	3,246			3,044
Accrued expenses and other liabilities	4,065			2,962
Total liabilities	155,896			153,736
Equity	23,979			23,141
Total liabilities and equity	179,875			176,877
Nonguarantors | Affiliated entity
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents, interest-bearing	1,044			521
Deposit liabilities, interest-bearing	$ 2,004			$ 1,249