Fair Value Measurements - Schedule of Fair Value Disclosures of Financial Instruments (Details) - USD ($) $ in Millions		Mar. 31, 2023	Dec. 31, 2022
ASSETS
Trading account assets		$ 1,118	$ 829
Derivative assets		397	1,024
Securities available for sale		39,498	39,117
Held to maturity securities		9,561	8,710
Loans, net of unearned income (residential)		119,971	119,394
Loans held for sale	[1]	1,211	963
LIABILITIES
Long-term debt, carrying amount		22,753	19,307
Carrying Amount
ASSETS
Trading account assets		1,118	829
Other investments		1,587	1,308
Loans, net of unearned income (residential)		9	9
Loans held for sale (residential)		45	24
Securities available for sale		39,498	39,117
Held to maturity securities		9,561	8,710
Loans, net of unearned income (residential)		118,582	118,048
Loans held for sale		1,166	939
Cash and other short-term investments		9,194	3,319
LIABILITIES
Time deposits, carrying amount		13,838	7,373
Short-term borrowings, carrying amount		11,435	9,463
Long-term debt, carrying amount		22,753	19,307
Deposits with no stated maturity		130,310	135,222
Carrying Amount | Derivatives Not Designated as Hedging Instruments
ASSETS
Derivative assets		382	927
LIABILITIES
Derivative liabilities		1,332	1,485
Carrying Amount | Derivatives Designated as Hedging Instruments
ASSETS
Derivative assets		15	97
LIABILITIES
Derivative liabilities		(38)	3
Fair Value
ASSETS
Trading account assets		1,118	829
Other investments		1,587	1,308
Loans, net of unearned income (residential)		9	9
Loans held for sale (residential)		45	24
Securities available for sale		39,498	39,117
Held to maturity securities		9,085	8,113
Loans, net of unearned income (residential)		112,964	112,590
Loans held for sale		1,166	939
Cash and other short-term investments		9,194	3,319
LIABILITIES
Time deposits, fair value		13,898	7,392
Short-term borrowings, fair value		11,435	9,463
Long-term debt, fair value		21,891	18,881
Deposits with no stated maturity		130,310	135,222
Fair Value | Derivatives Not Designated as Hedging Instruments
ASSETS
Derivative assets		382	927
Derivative assets, Netting Adjustment		(939)	(740)
LIABILITIES
Derivative liabilities		1,332	1,485
Derivative liabilities, Netting Adjustment		(835)	(1,262)
Fair Value | Derivatives Designated as Hedging Instruments
ASSETS
Derivative assets		15	97
Derivative assets, Netting Adjustment		(39)	(17)
LIABILITIES
Derivative liabilities		(38)	3
Derivative liabilities, Netting Adjustment		(15)	0
Fair Value | Level 1
ASSETS
Trading account assets		0	0
Other investments		3	4
Loans, net of unearned income (residential)		0	0
Loans held for sale (residential)		0	0
Securities available for sale		0	0
Held to maturity securities		0	0
Loans, net of unearned income (residential)		0	0
Loans held for sale		0	0
Cash and other short-term investments		9,194	3,319
LIABILITIES
Time deposits, fair value		0	0
Short-term borrowings, fair value		58	126
Long-term debt, fair value		12,195	12,196
Deposits with no stated maturity		0	0
Fair Value | Level 1 | Derivatives Not Designated as Hedging Instruments
ASSETS
Derivative assets		113	112
LIABILITIES
Derivative liabilities		95	107
Fair Value | Level 1 | Derivatives Designated as Hedging Instruments
ASSETS
Derivative assets		0	0
LIABILITIES
Derivative liabilities		0	0
Fair Value | Level 2
ASSETS
Trading account assets		1,118	829
Other investments		0	0
Loans, net of unearned income (residential)		0	0
Loans held for sale (residential)		45	24
Securities available for sale		39,498	39,117
Held to maturity securities		9,085	8,113
Loans, net of unearned income (residential)		0	0
Loans held for sale		0	0
Cash and other short-term investments		0	0
LIABILITIES
Time deposits, fair value		13,898	7,392
Short-term borrowings, fair value		11,377	9,337
Long-term debt, fair value		9,696	6,685
Deposits with no stated maturity		130,310	135,222
Fair Value | Level 2 | Derivatives Not Designated as Hedging Instruments
ASSETS
Derivative assets		1,193	1,552
LIABILITIES
Derivative liabilities		2,070	2,637
Fair Value | Level 2 | Derivatives Designated as Hedging Instruments
ASSETS
Derivative assets		54	114
LIABILITIES
Derivative liabilities		(23)	3
Fair Value | Level 3
ASSETS
Trading account assets		0	0
Other investments		1,530	1,234
Loans, net of unearned income (residential)		9	9
Loans held for sale (residential)		0	0
Securities available for sale		0	0
Held to maturity securities		0	0
Loans, net of unearned income (residential)		112,964	112,590
Loans held for sale		1,166	939
Cash and other short-term investments		0	0
LIABILITIES
Time deposits, fair value		0	0
Short-term borrowings, fair value		0	0
Long-term debt, fair value		0	0
Deposits with no stated maturity		0	0
Fair Value | Level 3 | Derivatives Not Designated as Hedging Instruments
ASSETS
Derivative assets		15	3
LIABILITIES
Derivative liabilities		2	3
Fair Value | Level 3 | Derivatives Designated as Hedging Instruments
ASSETS
Derivative assets		0	0
LIABILITIES
Derivative liabilities		0	0
Fair Value | Measured at NAV
ASSETS
Other investments		$ 54	$ 70

[1] Total loans held for sale include real estate — residential mortgage loans held for sale at fair value of $45 million at March 31, 2023, and $24 million at December 31, 2022.