Condensed Financial Information of the Parent Company - Condensed Balance Sheets (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Condensed Financial Statements, Captions [Line Items]
Cash and due from banks	$ 913	$ 1,091
Short-term investments	11,010	16,194
Securities available for sale	45,364	27,556
Other investments	639	621
Goodwill	2,693	2,664	$ 2,664
Corporate-owned life insurance	4,327	4,286
Derivative assets	1,962	1,798
Accrued income and other assets	8,265	6,812
Total assets	186,346	170,336
Accrued expense and other liabilities	3,548	2,385
Total long-term debt	12,042	13,709
Total liabilities	168,923	152,355
SHAREHOLDERS' EQUITY	17,423	17,981
Total liabilities and equity	186,346	170,336
Key
Condensed Financial Statements, Captions [Line Items]
Cash and due from banks	2,293	3,799
Short-term investments	24	21
Securities available for sale	0	12
Other investments	77	43
Total loans	66	66
Total investment in subsidiaries	18,034	18,545
Goodwill	167	167
Corporate-owned life insurance	212	207
Derivative assets	76	100
Accrued income and other assets	309	299
Total assets	21,258	23,259
Accrued expense and other liabilities	532	505
Long term debt due to Subsidiaries	483	500
Total long-term debt	3,303	4,773
Total liabilities	3,835	5,278
SHAREHOLDERS' EQUITY	17,423	17,981
Total liabilities and equity	21,258	23,259
Key | Banks
Condensed Financial Statements, Captions [Line Items]
Total loans	50	50
Investment in subsidiaries	17,019	17,645
Key | Nonbank subsidiaries
Condensed Financial Statements, Captions [Line Items]
Total loans	16	16
Investment in subsidiaries	1,015	900
Key | Unaffiliated companies
Condensed Financial Statements, Captions [Line Items]
Total long-term debt	$ 2,820	$ 4,273