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, 2017	$ 22,270	$ 3,196	$ 504	$ 9,799	$ 18,809		$ (1,009)		$ (9,029)
Beginning balance (shares) at Dec. 31, 2017			503,880						136,230
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	2,593				2,593
Other comprehensive income (loss)	(347)						(347)
Preferred stock issued	494	494
Common stock issued	1,150			586					$ 564
Common stock issued (in shares)									(13,244)
Cash dividends declared:
Common stock dividends	(665)				(665)
Preferred stock cash dividend	(188)				(188)
Common stock acquired (shares)									3,324
Common stock acquired	(350)								$ (350)
Common stock awards exercised (shares)									(2,389)
Common stock awards exercised	145			44					$ 101
Other (shares)									12
Other	(365)			(368)	4				$ (1)
Ending balance at Dec. 31, 2018	24,737	3,690	$ 504	10,061	20,553		(1,356)		$ (8,715)
Ending balance (shares) at Dec. 31, 2018			503,880						123,933
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	2,242				2,242
Reclassification of certain tax effects	(84)				84	[1]	(84)	[1]
Other comprehensive income (loss)	564						564
Preferred stock redeemed	(750)	(728)			(22)
Cash dividends declared:
Common stock dividends	(728)				(728)
Preferred stock cash dividend	(210)				(210)
Common stock acquired (shares)									24,884
Common stock acquired	(1,600)								$ (1,600)
Common stock awards exercised (shares)									(2,295)
Common stock awards exercised	198			95					$ 103
Other (shares)									(32)
Other	(22)			(24)	(1)				$ 3
Ending balance at Dec. 31, 2019	24,431	2,962	$ 504	10,132	21,918		(876)		$ (10,209)
Ending balance (shares) at Dec. 31, 2019			503,880						146,490
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	2,420				2,420
Other comprehensive income (loss)	1,063						1,063
Preferred stock redeemed	(500)	(491)			(9)
Cash dividends declared:
Common stock dividends	(734)				(734)
Preferred stock cash dividend	(152)				(152)
Common stock acquired (shares)									6,464
Common stock acquired	(500)								$ (500)
Common stock awards exercised (shares)									(2,233)
Common stock awards exercised	172			72					$ 100
Other (shares)									2
Other	0			1	(1)
Ending balance at Dec. 31, 2020	$ 26,200	$ 2,471	$ 504	$ 10,205	$ 23,442		$ 187		$ (10,609)
Ending balance (shares) at Dec. 31, 2020			503,880						150,723

[1] Represents the reclassification from accumulated other comprehensive income into retained earnings as a result of our adoption of ASU 2018-02 - Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income in the first quarter of 2019.