Consolidated Statement of Cash Flows - USD ($) $ in Millions	3 Months Ended				9 Months Ended		12 Months Ended
	Sep. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Operating Activities:
Net income	$ 583	$ 508	$ 764	$ 659	$ 1,678	$ 2,156
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Deferred income tax expense (benefit)					15	(91)
Amortization of other intangible assets	59		47		178	145	$ 226
Other non-cash adjustments for depreciation, amortization and accretion, net					796	729
(Gains) losses related to investment securities, net					1	(6)
Change in trading account assets, net					21	92
Change in accrued interest and fees receivable, net					(55)	(97)
Change in collateral deposits, net					216	7,236
Change in unrealized (gains) losses on foreign exchange derivatives, net					254	(2,118)
Change in other assets, net					(279)	47
Change in accrued expenses and other liabilities, net					1,471	873
Other, net					341	95
Net cash provided by operating activities					4,637	9,061
Investing Activities:
Net decrease in interest-bearing deposits with banks					10,716	3,609
Net decrease (increase) in securities purchased under resale agreements					1,638	(954)
Proceeds from sales of available-for-sale securities					5,185	15,712
Proceeds from maturities of available-for-sale securities					15,387	11,156
Purchases of available-for-sale securities					(30,204)	(17,949)
Proceeds from maturities of held-to-maturity securities					7,199	5,003
Purchases of held-to-maturity securities					(5,036)	(4,390)
Net increase in loans and leases					(1,220)	(53)
Business acquisitions, net of cash acquired					(54)	(63)
Purchases of equity investments and other long-term assets					(611)	(243)
Purchases of premises and equipment, net					(569)	(436)
Other, net					466	39
Net cash provided by investing activities					2,897	11,431
Financing Activities:
Net (decrease) increase in time deposits					(11,341)	1,606
Net increase (decrease) in all other deposits					1,868	(18,304)
Net increase (decrease) in other short-term borrowings					4,229	(1,287)
Payments for long-term debt and obligations under capital leases					(47)	(1,032)
Proceeds from issuance of preferred stock, net of issuance costs					0	495
Proceeds from issuance of common stock, net of issuance costs					0	1,150
Repurchases of common stock					(1,100)	(350)
Repurchases of common stock for employee tax withholding					(66)	113
Payments for cash dividends					(691)	(608)
Net cash used in financing activities					(7,148)	(18,217)
Net increase					386	2,275
Cash and due from banks at beginning of period		$ 3,212		$ 2,004	3,212	2,004	2,004
Cash and due from banks at end of period	$ 3,598		$ 4,279		$ 3,598	$ 4,279	$ 3,212