Business Segment Information - Amounts of Consolidated Revenue, Expense, Tax and Assets by Segment (Details) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2024	Mar. 31, 2024	Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2024	Jun. 30, 2023
Disaggregation of Revenue [Line Items]
Net interest income (expense)	$ 629		$ 630		$ 1,253	$ 1,318
Provision for credit losses	55		50		105	100
Noninterest income	186		400		381	571
Noninterest expense	500		555		1,015	1,033
Income (loss) before income taxes	260		425		514	756
Income tax expense (benefit)	56		96		113	171
Net income	204	$ 197	329	$ 255	401	585
Average assets	81,721		82,304		81,482	80,582
Gain on merger termination	0		225		0	225
Regional Banking
Disaggregation of Revenue [Line Items]
Net interest income (expense)	522		585		1,054	1,146
Provision for credit losses	57		36		86	72
Noninterest income	109		106		214	210
Noninterest expense	333		313		657	626
Income (loss) before income taxes	241		342		525	658
Income tax expense (benefit)	56		80		122	154
Net income	185		262		403	504
Average assets	43,519		42,302		43,283	41,800
Gain on merger termination			0			0
Specialty Banking
Disaggregation of Revenue [Line Items]
Net interest income (expense)	158		156		310	307
Provision for credit losses	1		18		23	33
Noninterest income	64		50		137	106
Noninterest expense	103		95		207	195
Income (loss) before income taxes	118		93		217	185
Income tax expense (benefit)	29		23		53	45
Net income	89		70		164	140
Average assets	24,592		23,329		24,194	22,978
Gain on merger termination			0			0
Corporate
Disaggregation of Revenue [Line Items]
Net interest income (expense)	(51)		(111)		(111)	(135)
Provision for credit losses	(3)		(4)		(4)	(5)
Noninterest income	13		244		30	255
Noninterest expense	64		147		151	212
Income (loss) before income taxes	(99)		(10)		(228)	(87)
Income tax expense (benefit)	(29)		(7)		(62)	(28)
Net income	(70)		(3)		(166)	(59)
Average assets	13,610		16,673		14,005	15,804
Restructuring costs	3				9
Special assessment fee	$ 2				$ 12
Gain on merger termination			225			225
Corporate | Visa Shares
Disaggregation of Revenue [Line Items]
Derivative valuation adjustment			15			15
Corporate | First Horizon Foundation
Disaggregation of Revenue [Line Items]
Charitable foundation contributions			50			50
Corporate | TD Transaction
Disaggregation of Revenue [Line Items]
Merger and integration expense			30			51
Gain on merger termination			$ 225			$ 225