Condensed Consolidated Balance Sheet & Mini Balance Sheet - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Assets [Abstract]
Cash and Due from Banks	$ 768	$ 844
Interest-bearing Deposits in Banks and Other Financial Institutions	2,953	3,408
Cash and Cash Equivalents, at Carrying Value	3,721	4,252
Equity Securities	680	518
Available-for-sale securities	22,726	22,303
Held-to-maturity securities	1,967	1,899
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group	126	108
Finance receivables and loans, net [Abstract]
Loans and Leases Receivable, Net of Deferred Income	125,327	122,893
Financing Receivable, Allowance for Credit Losses	1,278	1,276
Loans and Leases Receivable, Net Amount	124,049	121,617
Property Subject to or Available for Operating Lease, Net	8,530	8,741
Premiums receivable and other insurance assets	2,197	2,047
Other Assets	6,025	5,663
Assets	170,021	167,148
Liabilities and Equity [Abstract]
Noninterest-bearing deposit liabilities	122	108
Interest-bearing Deposit Liabilities	97,324	93,148
Deposits	97,446	93,256
Short-term Debt	9,564	11,413
Long-term Debt	45,076	44,226
Interest payable	494	375
Unearned Premiums	2,904	2,604
Accounts Payable and Accrued Liabilities	1,455	1,780
Liabilities	156,939	153,654
Equity [Abstract]
Common Stocks, Including Additional Paid in Capital, Net of Discount	21,273	21,245
Retained Earnings (Accumulated Deficit)	(6,318)	(6,406)
Accumulated Other Comprehensive Income (Loss), Net of Tax	(578)	(235)
Treasury stock, Value	(1,295)	(1,110)
Stockholders' Equity Attributable to Parent, Total	13,082	13,494
Liabilities and Equity	170,021	167,148
Variable Interest Entity, Primary Beneficiary [Member]
Finance receivables and loans, net [Abstract]
Loans and Leases Receivable, Net of Deferred Income	19,080	20,623
Financing Receivable, Allowance for Credit Losses	142	136
Loans and Leases Receivable, Net Amount	18,938	20,487
Property Subject to or Available for Operating Lease, Net	337	444
Other Assets	785	689
Assets	20,060	21,620
Liabilities and Equity [Abstract]
Long-term Debt	11,710	10,197
Accounts Payable and Accrued Liabilities	12	9
Liabilities	$ 11,722	$ 10,206