Consolidated Statement of Cash Flows - USD ($) $ in Millions	3 Months Ended				9 Months Ended		12 Months Ended
	Sep. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Mar. 31, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Operating Activities:
Net income	$ 730	$ 463	$ 422	$ 549	$ 1,904	$ 1,734
Adjustments to reconcile net income to net cash provided by operating activities:
Deferred income tax					57	8
Amortization of other intangible assets	56		60		176	180	$ 239
Other non-cash adjustments for depreciation, amortization and accretion, net					310	511
Losses related to investment securities, net					80	294
Provision for credit losses	26		0		63	26
Change in trading account assets, net					(29)	(75)
Change in accrued interest and fees receivable, net					(351)	(440)
Change in collateral deposits, net					(9,843)	(2,187)
Change in unrealized losses (gains) on foreign exchange derivatives, net					178	(2,748)
Change in other assets, net					183	(338)
Change in accrued expenses and other liabilities, net					1,324	(504)
Other, net					168	47
Net cash (used in) operating activities					(5,780)	(3,492)
Investing Activities:
Net (increase) decrease in interest-bearing deposits with banks					(17,456)	24,837
Net (increase) decrease in securities purchased under resale agreements					(1,642)	3,399
Proceeds from sales of available-for-sale securities	6,930				8,405	4,567
Proceeds from maturities of available-for-sale securities					13,280	11,870
Purchases of available-for-sale securities					(32,386)	(17,243)
Proceeds from maturities of held-to-maturity securities					7,718	4,414
Purchases of held-to-maturity securities					(5)	(1,579)
Sale of loans					223	465
Net increase in loans					(5,506)	(3,807)
Business acquisitions, net of cash acquired					(194)	0
Purchases of equity investments and other long-term assets					(104)	0
Purchases of premises and equipment, net					(677)	(487)
Other, net					(97)	130
Net cash (used in) provided by investing activities					(28,441)	26,566
Financing Activities:
Net (decrease) increase in time deposits					(4,646)	3,273
Net increase (decrease) in all other deposits					31,105	(25,729)
Net increase in securities sold under repurchase agreements					252	1,920
Net increase (decrease) in other short-term borrowings					6,358	(2,089)
Proceeds from issuance of long-term debt, net of issuance costs					1,992	4,729
Payments for long-term debt and obligations under finance leases					(35)	(1,037)
Payments for redemption of preferred stock					(1,500)	0
Proceeds from issuance of preferred stock, net of issuance costs					2,323	0
Repurchases of common stock					(769)	(3,300)
Repurchases of common stock for employee tax withholding					(68)	(83)
Payments for cash dividends					(755)	(719)
Other, net					(16)	0
Net cash provided by (used in) financing activities					34,241	(23,035)
Net increase in cash and due from banks					20	39
Cash and due from banks at beginning of period		$ 4,047		$ 3,970	4,047	3,970	3,970
Cash and due from banks at end of period	$ 4,067		$ 4,009		4,067	4,009	$ 4,047
Supplemental disclosure:
Interest paid					6,593	4,320
Income taxes paid, net					$ 345	$ 258