Condensed Consolidated Balance Sheet & Mini Balance Sheet - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Assets [Abstract]
Cash and cash equivalents, noninterest-bearing	$ 802	$ 844
Cash and cash equivalents, interest-bearing	2,970	3,408
Total cash and cash equivalents	3,772	4,252
Equity securities	514	518
Available-for-sale securities	24,122	22,303
Held-to-maturity securities	2,246	1,899
Loans held-for-sale, net	425	108
Finance receivables and loans, net [Abstract]
Finance receivables and loans, net of unearned income	126,605	122,893
Allowance for loan losses	1,248	1,276
Total finance receivables and loans, net	125,357	121,617
Investment in operating leases, net	8,578	8,741
Premiums receivable and other insurance assets	2,291	2,047
Other assets	5,796	5,663
Total assets	173,101	167,148
Liabilities and Equity [Abstract]
Deposit liabilities, noninterest-bearing	180	108
Deposit liabilities, interest-bearing	101,199	93,148
Total deposit liabilities	101,379	93,256
Short-term borrowings	7,338	11,413
Long-term debt	45,542	44,226
Interest payable	712	375
Unearned insurance premiums and service revenue	3,020	2,604
Accrued expenses and other liabilities	2,025	1,780
Total liabilities	160,016	153,654
Equity [Abstract]
Common stock and paid-in capital	21,322	21,245
Accumulated deficit	(5,716)	(6,406)
Accumulated other comprehensive loss	(781)	(235)
Treasury stock, at cost	(1,740)	(1,110)
Total equity	13,085	13,494
Total liabilities and equity	173,101	167,148
Variable Interest Entity, Primary Beneficiary
Finance receivables and loans, net [Abstract]
Finance receivables and loans, net of unearned income	17,694	20,623
Allowance for loan losses	123	136
Total finance receivables and loans, net	17,571	20,487
Investment in operating leases, net	206	444
Other assets	622	689
Total assets	18,399	21,620
Liabilities and Equity [Abstract]
Long-term debt	11,457	10,197
Accrued expenses and other liabilities	26	9
Total liabilities	$ 11,483	$ 10,206