Consolidated Statements Of Changes In Shareholders' Equity (unaudited) - USD ($) shares in Millions, $ in Millions		Total	Nonredeemable Preferred Stock	Common Stock	Capital Surplus	Accumulated Other Comprehensive Loss	Retained Earnings	Treasury Stock
Beginning balance (in shares) at Dec. 31, 2022				131.0
Balance at Dec. 31, 2022		$ 5,181	$ 394	$ 1,141	$ 2,220	$ (3,742)	$ 11,258	$ (6,090)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		597					597
Other comprehensive income (loss), net of tax		(14)				(14)
Cash dividends declared on common stock		(188)					(188)
Cash dividends declared on preferred stock		(11)					(11)
Net issuance of common stock under employee stock plans (in shares)				0.7
Net issuance of common stock under employee stock plans		(5)			(43)		(8)	46
Share-based compensation		35			35
Ending balance at Jun. 30, 2023		5,595	394	$ 1,141	2,212	(3,756)	11,648	(6,044)
Ending Balance (in shares) at Jun. 30, 2023				131.7
Beginning balance (in shares) at Mar. 31, 2023				131.5
Balance at Mar. 31, 2023		5,994	394	$ 1,141	2,209	(3,171)	11,476	(6,055)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		273					273
Other comprehensive income (loss), net of tax		(585)				(585)
Cash dividends declared on common stock		(94)					(94)
Cash dividends declared on preferred stock		(5)					(5)
Net issuance of common stock under employee stock plans (in shares)				0.2
Net issuance of common stock under employee stock plans		5			(4)		(2)	11
Share-based compensation		7			7
Ending balance at Jun. 30, 2023		5,595	394	$ 1,141	2,212	(3,756)	11,648	(6,044)
Ending Balance (in shares) at Jun. 30, 2023				131.7
Beginning balance (in shares) at Dec. 31, 2023				131.9
Balance at Dec. 31, 2023		6,406	394	$ 1,141	2,224	(3,048)	11,727	(6,032)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of change in accounting principle	[1]	(4)					(4)
Net income		344					344
Other comprehensive income (loss), net of tax		(415)				(415)
Cash dividends declared on common stock		(189)					(189)
Cash dividends declared on preferred stock		(11)					(11)
Net issuance of common stock under employee stock plans (in shares)				0.7
Net issuance of common stock under employee stock plans		(6)			(50)		0	44
Share-based compensation		36			36
Ending balance at Jun. 30, 2024		6,161	394	$ 1,141	2,210	(3,463)	11,867	(5,988)
Ending Balance (in shares) at Jun. 30, 2024				132.6
Beginning balance (in shares) at Mar. 31, 2024				132.5
Balance at Mar. 31, 2024		6,050	394	$ 1,141	2,202	(3,457)	11,765	(5,995)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		206					206
Other comprehensive income (loss), net of tax		(6)				(6)
Cash dividends declared on common stock		(95)					(95)
Cash dividends declared on preferred stock		(5)					(5)
Net issuance of common stock under employee stock plans (in shares)				0.1
Net issuance of common stock under employee stock plans		2			(1)		(4)	7
Share-based compensation		9			9
Ending balance at Jun. 30, 2024		$ 6,161	$ 394	$ 1,141	$ 2,210	$ (3,463)	$ 11,867	$ (5,988)
Ending Balance (in shares) at Jun. 30, 2024				132.6

[1] Effective January 1, 2024, the Corporation adopted ASU 2023-02, which expanded the permitted use of the proportional amortization method to certain tax credit investments.