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]			0	(1)	[1]		$ 0
Other (shares)	[1]									(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
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		1,328
Other comprehensive income (loss)		446
Cash dividends declared:
Common stock dividends		(366)
Preferred stock cash dividend		(76)
Ending balance at Jun. 30, 2020		24,873		2,471	$ 504	10,179	22,794		(430)	$ (10,645)
Ending balance (shares) at Jun. 30, 2020					503,880					151,496
Cash dividends declared:
Retained earnings | Accounting Standards Update 2016-13		3
Beginning balance at Mar. 31, 2020		23,861		2,471	$ 504	10,155	22,315		(920)	$ (10,664)
Beginning balance (shares) at Mar. 31, 2020					503,880					151,936
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		694					694
Other comprehensive income (loss)		490							490
Cash dividends declared:
Common stock dividends		(183)					(183)
Preferred stock cash dividend		(32)					(32)
Common stock acquired (shares)
Common stock acquired		0
Common stock awards exercised		44				24				$ 20
Common stock awards exercised (shares)										(443)
Other		(1)								$ (1)
Other (shares)										(3)
Ending balance at Jun. 30, 2020		24,873		2,471	$ 504	10,179	22,794		(430)	$ (10,645)
Ending balance (shares) at Jun. 30, 2020					503,880					151,496
Cash dividends declared:
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
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		1,282
Other comprehensive income (loss)		(609)
Cash dividends declared:
Common stock dividends		(361)
Preferred stock cash dividend		(59)
Ending balance at Jun. 30, 2021		25,167		1,976	$ 504	10,246	24,300		(422)	$ (11,437)
Ending balance (shares) at Jun. 30, 2021					503,880					160,377
Beginning balance at Mar. 31, 2021		25,005		1,976	$ 504	10,227	23,751		(418)	$ (11,035)
Beginning balance (shares) at Mar. 31, 2021					503,880					155,847
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		763					763
Other comprehensive income (loss)		(4)							(4)
Cash dividends declared:
Common stock dividends		(179)					(179)
Preferred stock cash dividend		(34)					(34)
Common stock acquired (shares)										5,017
Common stock acquired		(425)								$ (425)
Common stock awards exercised		42				19				$ 23
Common stock awards exercised (shares)										(487)
Other		(1)					(1)
Other (shares)
Ending balance at Jun. 30, 2021		25,167		$ 1,976	$ 504	$ 10,246	$ 24,300		$ (422)	$ (11,437)
Ending balance (shares) at Jun. 30, 2021					503,880					160,377
Cash dividends declared:
Retained earnings		$ (24,300)

[1] Includes the impact of transitioning to ASC 326: Measurement of Credit Losses on Financial Instruments, consisting of a decrease in retained earnings of $3 million in the first quarter of 2020.