Parent Company (Statement of Cash Flows) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Other operating activities, net		$ 1,197	$ 838	$ (258)
Net cash provided (used) by operating activities		10,111	9,083	7,214
Investing Activities
Securities available for sale		36	4,137	26,329
Net cash paid for acquisition	[1]			(10,511)
Other investing activities, net		(1,950)	(2,995)	(2,682)
Net cash provided (used) by investing activities		(6,379)	(13,428)	(2,795)
Financing Activities
Preferred stock issuances		1,484	2,225	1,484
Preferred stock redemptions		(1,000)	(1,500)
Acquisition of treasury stock		(651)	(3,731)	(1,079)
Preferred stock cash dividends paid		(417)	(301)	(233)
Common stock cash dividends paid		(2,461)	(2,391)	(2,056)
Net Increase (Decrease) In Cash And Due From Banks And Restricted Cash		(122)	(961)	987
Cash and due from banks and restricted cash at beginning of period		7,043	8,004	7,017
Cash and due from banks and restricted cash at end of period		6,921	7,043	8,004
Parent Company
Operating Activities
Net income		5,578	6,041	5,673
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Equity in undistributed net earnings of subsidiaries		(3,176)	(2,303)	(1,628)
Other operating activities, net		1,276	95	(248)
Net cash provided (used) by operating activities		3,678	3,833	3,797
Investing Activities
Securities available for sale				300
Net change in loans and securities from affiliates		(9,475)	(531)	(1,188)
Net cash paid for acquisition				(11,358)
Other investing activities, net		(5)	(84)	(5)
Net cash provided (used) by investing activities		(9,480)	(615)	(12,251)
Financing Activities
Net change in other borrowed funds from affiliates		255	(1,138)	(435)
Proceeds from long-term borrowings		10,463	4,335	1,692
Repayments of long-term borrowings			(1,500)	(500)
Preferred stock issuances		1,484	2,225	1,484
Preferred stock redemptions		(1,000)	(1,500)
Common and treasury stock issuances		72	68	66
Acquisition of treasury stock		(651)	(3,731)	(1,079)
Preferred stock cash dividends paid		(417)	(301)	(233)
Common stock cash dividends paid		(2,459)	(2,389)	(2,056)
Net cash provided (used) by financing activities		7,747	(3,931)	(1,061)
Net Increase (Decrease) In Cash And Due From Banks And Restricted Cash		1,945	(713)	(9,515)
Cash and due from banks and restricted cash at beginning of period		4,829	5,542	15,057
Cash and due from banks and restricted cash at end of period		$ 6,774	$ 4,829	$ 5,542

[1] During the year ended December 31, 2021, cash paid to acquire BBVA was $11,480 million. The amount of $10,511 million represents the cash paid for the acquisition less $969 million in cash acquired.