Fair Value Measurements - Schedule of Fair Value Disclosures of Financial Instruments (Details) - USD ($) $ in Millions		Sep. 30, 2025	Dec. 31, 2024
ASSETS
Trading account assets		$ 972	$ 1,283
Derivative assets		230	249
Securities available for sale		40,456	37,707
Held to maturity securities		7,509	7,395
Loans, net of unearned income (residential)		105,902	104,260
Loans held for sale	[1]	998	797
LIABILITIES
Long-term debt, carrying amount		10,917	12,105
Carrying Amount
ASSETS
Trading account assets		972	1,283
Other investments		921	1,041
Loans, net of unearned income (residential)		10	10
Loans held for sale (residential)		62	93
Securities available for sale		40,456	37,707
Held to maturity securities		7,509	7,395
Loans, net of unearned income (residential)		104,448	102,841
Loans held for sale		936	704
Cash and other short-term investments		15,272	19,247
LIABILITIES
Time deposits, carrying amount		14,595	16,952
Short-term borrowings, carrying amount		1,349	2,144
Long-term debt, carrying amount		10,917	12,105
Deposits with no stated maturity		136,170	132,808
Carrying Amount | Derivative assets/liabilities - trading
ASSETS
Derivative assets		213	255
LIABILITIES
Derivative liabilities		637	1,028
Carrying Amount | Derivative assets/liabilities - hedging
ASSETS
Derivative assets		17	(6)
LIABILITIES
Derivative liabilities		0	0
Fair Value
ASSETS
Trading account assets		972	1,283
Other investments		921	1,041
Loans, net of unearned income (residential)		10	10
Loans held for sale (residential)		62	93
Securities available for sale		40,456	37,707
Held to maturity securities		7,164	6,837
Loans, net of unearned income (residential)		101,186	99,105
Loans held for sale		936	704
Cash and other short-term investments		15,272	19,247
LIABILITIES
Time deposits, fair value		14,675	17,068
Short-term borrowings, fair value		1,349	2,144
Long-term debt, fair value		11,026	11,907
Deposits with no stated maturity		136,170	132,808
Fair Value | Derivative assets/liabilities - trading
ASSETS
Derivative assets		213	255
Derivative assets, Netting Adjustment		(329)	(361)
LIABILITIES
Derivative liabilities		637	1,028
Derivative liabilities, Netting Adjustment		(334)	(408)
Fair Value | Derivative assets/liabilities - hedging
ASSETS
Derivative assets		17	(6)
Derivative assets, Netting Adjustment			(2)
LIABILITIES
Derivative liabilities		0	0
Derivative liabilities, Netting Adjustment			(3)
Fair Value | Level 1
ASSETS
Trading account assets		1	0
Other investments		0	0
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		15,272	19,247
LIABILITIES
Time deposits, fair value		0	0
Short-term borrowings, fair value		484	107
Long-term debt, fair value		10,275	11,430
Deposits with no stated maturity		0	0
Fair Value | Level 1 | Derivative assets/liabilities - trading
ASSETS
Derivative assets		57	93
LIABILITIES
Derivative liabilities		51	85
Fair Value | Level 1 | Derivative assets/liabilities - hedging
ASSETS
Derivative assets		0	0
LIABILITIES
Derivative liabilities		0	0
Fair Value | Level 2
ASSETS
Trading account assets		971	1,283
Other investments		0	0
Loans, net of unearned income (residential)		0	0
Loans held for sale (residential)		62	93
Securities available for sale		40,456	37,707
Held to maturity securities		7,164	6,837
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		14,675	17,068
Short-term borrowings, fair value		865	2,037
Long-term debt, fair value		751	477
Deposits with no stated maturity		136,170	132,808
Fair Value | Level 2 | Derivative assets/liabilities - trading
ASSETS
Derivative assets		481	527
LIABILITIES
Derivative liabilities		920	1,351
Fair Value | Level 2 | Derivative assets/liabilities - hedging
ASSETS
Derivative assets		17	(4)
LIABILITIES
Derivative liabilities		0	3
Fair Value | Level 3
ASSETS
Trading account assets		0	0
Other investments		839	969
Loans, net of unearned income (residential)		10	10
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)		101,186	99,105
Loans held for sale		936	704
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 | Derivative assets/liabilities - trading
ASSETS
Derivative assets		4	(4)
LIABILITIES
Derivative liabilities		0	0
Fair Value | Level 3 | Derivative assets/liabilities - hedging
ASSETS
Derivative assets		0	0
LIABILITIES
Derivative liabilities		0	0
Fair Value | Measured at NAV
ASSETS
Other investments		$ 82	$ 72

[1] Total loans held for sale include real estate — residential mortgage loans held for sale at fair value of $62 million at September 30, 2025, and $93 million at December 31, 2024.