Condensed Consolidated Statement of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Net Cash Provided by (Used in) Operating Activities [Abstract]
Net Income (Loss) Attributable to Parent	$ 250	$ 214
Depreciation, Amortization and Accretion, Net	434	534
Provision for Loan Losses Expensed Including Discontinued Operations	261	271
Gain Loss on Sales of Loans Net Including Discontinued Operations	(1)	(14)
Availableforsale Securities Gross Realized Gain Loss Excluding Otti Including Disc Ops	12	(27)
Payments for Origination and Purchases of Loans Held-for-sale	(248)	(21)
Proceeds from Sale of Loans Held-for-sale	230	20
Increase (Decrease) in Deferred Income Taxes	83	91
Increase (Decrease) in Interest Payable, Net	120	31
Increase (Decrease) in Other Operating Assets	29	60
Increase (Decrease) in Other Operating Liabilities	(106)	(20)
Increase (Decrease) in Other Operating Assets and Liabilities, Net	33	36
Net Cash Provided by (Used in) Operating Activities	1,097	1,175
Net Cash (Used in) Provided by Investing Activities [Abstract]
Purchases of Equity Securities	(374)	(137)
Proceeds from Sales of Equity Securities	220	314
Payments to Acquire Available-for-sale Securities	(2,360)	(2,696)
Proceeds from Sale of Available-for-sale Securities	328	731
Proceeds from maturities and repayment of available-for-sale securities	795	589
Payments to Acquire Held-to-maturity Securities	(155)	(215)
Proceeds from Sale and Maturity of Held-to-maturity Securities	35	5
Payments for (Proceeds from) Loans and Leases	(1,497)	(405)
Proceeds from Sale of Loans Held-for-investment	0	1,164
Originations and repayments of loans held-for-investment and other	(1,300)	(1,174)
Purchases of operating lease assets	(969)	(893)
Disposals of Operating Lease Assets	976	1,545
Increase (Decrease) in Non marketable equity securities	(19)	213
Payments for (Proceeds from) Other Investing Activities	(82)	(56)
Net cash provided by investing activities	(4,402)	(1,015)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Proceeds from (Repayments of) Short-term Debt	(1,848)	(4,303)
Increase (Decrease) in Deposits	4,173	5,451
Proceeds from Issuance of Long-term Debt	6,665	4,488
Repayments of long-term debt	(5,771)	(7,573)
Payments for Repurchase of Common Stock	(185)	(169)
Payments of Dividends	(58)	(38)
Net cash (used in) provided by financing activities	2,976	(2,144)
Effect of Exchange Rate on Cash and Cash Equivalents	(2)	0
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect	(331)	(1,984)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	4,938	5,897
Cash and Cash Equivalents, at Carrying Value	3,721	4,302
Restricted Cash	1,217	1,595
Supplemental Cash Flow Information [Abstract]
Interest Paid	667	648
Income Taxes Paid	5	2
Held-to-maturity securities received in consideration for loans sold	0	56
Transfer of Portfolio Loans and Leases to Held-for-sale	0	1,213
Proceeds from sales and repayments of mortgage loans held-for-investment originally designated as held-for-sale	$ 11	$ 8