Consolidated Balance Sheet & Mini Balance Sheet - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Assets [Abstract]
Cash and Due from Banks	$ 844	$ 1,547
Interest-bearing Deposits in Banks and Other Financial Institutions	3,408	4,387
Cash and Cash Equivalents, at Carrying Value	4,252	5,934
Available-for-sale securities	22,821	18,926
Held-to-maturity securities	1,899	839
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group	108	0
Finance receivables and loans, net [Abstract]
Loans and Leases Receivable, Net of Deferred Income	122,893	118,944
Financing Receivable, Allowance for Credit Losses	1,276	1,144
Loans and Leases Receivable, Net Amount	121,617	117,800
Property Subject to or Available for Operating Lease, Net	8,741	11,470
Premiums receivable and other insurance assets	2,047	1,905
Other Assets	5,663	6,854
Assets	167,148	163,728
Liabilities and Equity [Abstract]
Noninterest-bearing deposit liabilities	108	84
Interest-bearing Deposit Liabilities	93,148	78,938
Deposits	93,256	79,022
Short-term Debt	11,413	12,673
Long-term Debt	44,226	54,128
Interest payable	375	351
Unearned Premiums	2,604	2,500
Accounts Payable and Accrued Liabilities	1,780	1,737
Liabilities	153,654	150,411
Equity [Abstract]
Common Stocks, Including Additional Paid in Capital, Net of Discount	21,245	21,166
Retained Earnings (Accumulated Deficit)	(6,406)	(7,151)
Accumulated Other Comprehensive Income (Loss), Net of Tax	(235)	(341)
Treasury stock, Value	(1,110)	(357)
Stockholders' Equity Attributable to Parent, Total	13,494	13,317
Liabilities and Equity	167,148	163,728
Variable Interest Entity, Primary Beneficiary [Member]
Finance receivables and loans, net [Abstract]
Loans and Leases Receivable, Net of Deferred Income	20,623	24,630
Financing Receivable, Allowance for Credit Losses	136	173
Loans and Leases Receivable, Net Amount	20,487	24,457
Property Subject to or Available for Operating Lease, Net	444	1,745
Other Assets	689	1,390
Assets	21,620	27,592
Liabilities and Equity [Abstract]
Long-term Debt	10,197	13,259
Accounts Payable and Accrued Liabilities	9	12
Liabilities	$ 10,206	$ 13,271