Condensed Consolidated Balance Sheet & Mini Balance Sheet - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Assets [Abstract]
Cash and Due from Banks	$ 799	$ 844
Interest-bearing Deposits in Banks and Other Financial Institutions	3,125	3,408
Cash and Cash Equivalents, at Carrying Value	3,924	4,252
Marketable Securities, Equity Securities	521	518
Available-for-sale securities	23,296	22,303
Held-to-maturity securities	2,089	1,899
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group	328	108
Finance receivables and loans, net [Abstract]
Loans and Leases Receivable, Net of Deferred Income	125,544	122,893
Financing Receivable, Allowance for Credit Losses	1,257	1,276
Loans and Leases Receivable, Net Amount	124,287	121,617
Property Subject to or Available for Operating Lease, Net	8,639	8,741
Premiums receivable and other insurance assets	2,247	2,047
Other Assets	6,014	5,663
Assets	171,345	167,148
Liabilities and Equity [Abstract]
Noninterest-bearing deposit liabilities	153	108
Interest-bearing Deposit Liabilities	98,581	93,148
Deposits	98,734	93,256
Short-term Debt	7,108	11,413
Long-term Debt	47,328	44,226
Interest payable	568	375
Unearned Premiums	2,957	2,604
Accounts Payable and Accrued Liabilities	1,511	1,780
Liabilities	158,206	153,654
Equity [Abstract]
Common Stocks, Including Additional Paid in Capital, Net of Discount	21,303	21,245
Retained Earnings (Accumulated Deficit)	(6,026)	(6,406)
Accumulated Other Comprehensive Income (Loss), Net of Tax	(648)	(235)
Treasury stock, Value	(1,490)	(1,110)
Stockholders' Equity Attributable to Parent, Total	13,139	13,494
Liabilities and Equity	171,345	167,148
Variable Interest Entity, Primary Beneficiary [Member]
Finance receivables and loans, net [Abstract]
Loans and Leases Receivable, Net of Deferred Income	19,386	20,623
Financing Receivable, Allowance for Credit Losses	146	136
Loans and Leases Receivable, Net Amount	19,240	20,487
Property Subject to or Available for Operating Lease, Net	257	444
Other Assets	722	689
Assets	20,219	21,620
Liabilities and Equity [Abstract]
Long-term Debt	12,345	10,197
Accounts Payable and Accrued Liabilities	12	9
Liabilities	$ 12,357	$ 10,206