Consolidated Statement of Changes In Shareholders' Equity - USD ($) shares in Thousands, $ in Millions	Total	Preferred Stock	Common Stock	Surplus	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock
Beginning balance at Dec. 31, 2019	$ 24,431	$ 2,962	$ 504	$ 10,132	$ 21,918	$ (876)	$ (10,209)
Beginning balance (shares) at Dec. 31, 2019			503,880				146,490
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	634				634
Other comprehensive income (loss)	(44)					(44)
Preferred stock redeemed	(500)	(491)			(9)
Cash dividends declared:
Common stock dividends	(183)				(183)
Preferred stock cash dividend	(44)				(44)
Common stock acquired (shares)							6,464
Common stock acquired	(500)						$ (500)
Common stock awards exercised	68			23			$ 45
Common stock awards exercised (shares)							(1,017)
Other	(1)				(1)
Other (shares)							(1)
Ending balance at Mar. 31, 2020	23,861	2,471	$ 504	10,155	22,315	(920)	$ (10,664)
Ending balance (shares) at Mar. 31, 2020			503,880				151,936
Cash dividends declared:
Retained earnings | Accounting Standards Update 2016-13	3
Retained earnings	(23,442)
Beginning balance at Dec. 31, 2020	26,200	2,471	$ 504	10,205	23,442	187	$ (10,609)
Beginning balance (shares) at Dec. 31, 2020			503,880				150,723
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	519				519
Other comprehensive income (loss)	(605)					(605)
Preferred stock redeemed	(500)	(495)			(5)
Cash dividends declared:
Common stock dividends	(182)				(182)
Preferred stock cash dividend	(25)				(25)
Common stock acquired (shares)							6,233
Common stock acquired	(475)						$ (475)
Common stock awards exercised	71			22			$ 49
Common stock awards exercised (shares)							(1,111)
Other	2				2
Other (shares)							2
Ending balance at Mar. 31, 2021	25,005	$ 1,976	$ 504	$ 10,227	$ 23,751	$ (418)	$ (11,035)
Ending balance (shares) at Mar. 31, 2021			503,880				155,847
Cash dividends declared:
Retained earnings	$ (23,751)