Fair Value Measurements - Schedule of Fair Value Disclosures of Financial Instruments (Details) - USD ($) $ in Millions		Jun. 30, 2024	Dec. 31, 2023
ASSETS
Trading account assets		$ 1,219	$ 1,142
Derivative assets		230	181
Securities available for sale		37,460	37,185
Held to maturity securities		7,968	8,575
Loans, net of unearned income (residential)		107,078	112,606
Loans held for sale	[1]	517	483
LIABILITIES
Long-term debt, carrying amount		16,869	19,554
Carrying Amount
ASSETS
Trading account assets		1,219	1,142
Other investments		1,259	1,244
Loans, net of unearned income (residential)		11	9
Loans held for sale (residential)		91	51
Securities available for sale		37,460	37,185
Held to maturity securities		7,968	8,575
Loans, net of unearned income (residential)		105,520	111,089
Loans held for sale		426	432
Cash and other short-term investments		16,862	11,758
LIABILITIES
Time deposits, carrying amount		17,652	14,776
Short-term borrowings, carrying amount		5,317	3,091
Long-term debt, carrying amount		16,869	19,554
Deposits with no stated maturity		128,068	130,811
Carrying Amount | Derivatives Not Designated as Hedging Instruments
ASSETS
Derivative assets		225	168
LIABILITIES
Derivative liabilities		1,204	1,304
Carrying Amount | Derivatives Designated as Hedging Instruments
ASSETS
Derivative assets		5	13
LIABILITIES
Derivative liabilities		6	0
Fair Value
ASSETS
Trading account assets		1,219	1,142
Other investments		1,259	1,244
Loans, net of unearned income (residential)		11	9
Loans held for sale (residential)		91	51
Securities available for sale		37,460	37,185
Held to maturity securities		7,358	8,056
Loans, net of unearned income (residential)		101,340	105,950
Loans held for sale		426	432
Cash and other short-term investments		16,862	11,758
LIABILITIES
Time deposits, fair value		17,807	14,911
Short-term borrowings, fair value		5,317	3,091
Long-term debt, fair value		16,343	19,008
Deposits with no stated maturity		128,068	130,811
Fair Value | Derivatives Not Designated as Hedging Instruments
ASSETS
Derivative assets		225	168
Derivative assets, Netting Adjustment		(533)	(792)
LIABILITIES
Derivative liabilities		1,204	1,304
Derivative liabilities, Netting Adjustment		(463)	(461)
Fair Value | Derivatives Designated as Hedging Instruments
ASSETS
Derivative assets		5	13
Derivative assets, Netting Adjustment		1	(26)
LIABILITIES
Derivative liabilities		6	0
Derivative liabilities, Netting Adjustment		(3)	(12)
Fair Value | Level 1
ASSETS
Trading account assets		52	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		16,862	11,758
LIABILITIES
Time deposits, fair value		0	0
Short-term borrowings, fair value		28	30
Long-term debt, fair value		11,010	11,288
Deposits with no stated maturity		0	0
Fair Value | Level 1 | Derivatives Not Designated as Hedging Instruments
ASSETS
Derivative assets		74	74
LIABILITIES
Derivative liabilities		54	58
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		1,167	1,142
Other investments		6	0
Loans, net of unearned income (residential)		0	0
Loans held for sale (residential)		91	51
Securities available for sale		37,460	37,185
Held to maturity securities		7,358	8,056
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		17,807	14,911
Short-term borrowings, fair value		5,289	3,061
Long-term debt, fair value		5,333	7,720
Deposits with no stated maturity		128,068	130,811
Fair Value | Level 2 | Derivatives Not Designated as Hedging Instruments
ASSETS
Derivative assets		685	886
LIABILITIES
Derivative liabilities		1,613	1,707
Fair Value | Level 2 | Derivatives Designated as Hedging Instruments
ASSETS
Derivative assets		4	39
LIABILITIES
Derivative liabilities		9	12
Fair Value | Level 3
ASSETS
Trading account assets		0	0
Other investments		1,191	1,183
Loans, net of unearned income (residential)		11	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)		101,340	105,950
Loans held for sale		426	432
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		(1)	0
LIABILITIES
Derivative liabilities		0	0
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		$ 62	$ 61

[1] Total loans held for sale include real estate — residential mortgage loans held for sale at fair value of $91 million at June 30, 2024, and $51 million at December 31, 2023.