Consolidated Statement of Cash Flows - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Operating Activities:
Net income	$ 519	$ 634
Adjustments to reconcile net income to net cash provided by operating activities:
Deferred income tax (benefit)	(26)	8
Amortization of other intangible assets	58	58	$ 234
Other non-cash adjustments for depreciation, amortization and accretion, net	359	274
Losses (gains) related to investment securities, net	0	(2)
Provision for credit losses	(9)	36
Change in trading account assets, net	29	42
Change in accrued interest and fees receivable, net	(197)	(43)
Change in collateral deposits, net	35	2,685
Change in unrealized losses (gains) on foreign exchange derivatives, net	(6,250)	(3,090)
Change in other assets, net	(377)	(891)
Change in accrued expenses and other liabilities, net	2,000	4,179
Other, net	127	149
Net cash (used in) provided by operating activities	(3,732)	4,039
Investing Activities:
Net (increase) decrease in interest-bearing deposits with banks	9,406	(78,770)
Net (increase) decrease in securities purchased under resale agreements	(2,132)	450
Proceeds from sales of available-for-sale securities	5,168	1,657
Proceeds from maturities of available-for-sale securities	5,004	4,219
Purchases of available-for-sale securities	(12,324)	(8,935)
Purchases of held-to-maturity securities under the MMLF program	0	(26,061)
Proceeds from maturities of held-to-maturity securities under the MMLF program	3,099	451
Proceeds from maturities of held-to-maturity securities	3,840	2,695
Purchases of held-to-maturity securities	(1,268)	(2,141)
Sale of loans	35	93
Net (increase) in loans	(3,695)	(6,164)
Business acquisitions, net of cash acquired	(214)	0
Purchases of equity investments and other long-term assets	(34)	(794)
Purchases of premises and equipment, net	(162)	(114)
Other, net	81	641
Net cash provided by (used in) investing activities	6,804	(112,773)
Financing Activities:
Net (decrease) increase in time deposits	(1,580)	18,635
Net increase (decrease) in all other deposits	6,674	56,596
Net (decrease) increase in securities sold under repurchase agreements	(2,826)	4,271
Net (decrease) increase in short-term borrowings under money market liquidity facility	(3,102)	25,665
Net (decrease) increase in other short-term borrowings	(43)	3,996
Proceeds from issuance of long-term debt, net of issuance costs	844	2,497
Payments for long-term debt and obligations under finance leases	(764)	(8)
Payments for redemption of preferred stock	(500)	(500)
Repurchases of common stock	(475)	(515)
Repurchases of common stock for employee tax withholding	(6)	(43)
Payments for cash dividends	(209)	(230)
Net cash (used in) provided by financing activities	(1,987)	110,364
Net increase	1,085	1,630
Cash and due from banks at beginning of period	3,467	3,302	3,302
Cash and due from banks at end of period	$ 4,552	$ 4,932	$ 3,467