Fair Value Measurements - Fair Value Disclosures of Financial Instruments (Details) - USD ($) $ in Millions		Sep. 30, 2022	Dec. 31, 2021
ASSETS
Trading account assets		$ 1,068	$ 701
Derivative assets		1,601	1,962
Securities available for sale		40,000	45,364
Held to maturity securities		8,163	7,539
Loans, net of unearned income		116,191	101,854
Loans held for sale	[1]	1,048	2,729
LIABILITIES
Long-term debt		18,257	12,042
Carrying Amount
ASSETS
Trading account assets		1,068	701
Other investments		1,272	639
Loans, net of unearned income (residential)		9	11
Loans held for sale		61	281
Securities available for sale		40,000	45,364
Held to maturity securities		8,163	7,539
Loans, net of unearned income		115,038	100,782
Loans held for sale		987	2,448
Short-term investments			0
Cash and short-term investments		5,613	11,923
LIABILITIES
Time deposits		5,847	3,858
Short-term borrowings		8,800	761
Long-term debt		18,257	12,042
Deposits with no stated maturity		139,008	148,714
Carrying Amount | Derivatives Not Designated as Hedging Instruments
ASSETS
Derivative assets		1,535	1,887
LIABILITIES
Derivative liabilities		1,590	157
Carrying Amount | Derivatives Designated as Hedging Instruments
ASSETS
Derivative assets		66	75
LIABILITIES
Derivative liabilities		10	4
Fair Value
ASSETS
Trading account assets		1,068	701
Other investments		1,272	639
Loans, net of unearned income (residential)		9	11
Loans held for sale		61	281
Securities available for sale		40,000	45,364
Held to maturity securities		7,596	7,665
Loans, net of unearned income		109,738	100,428
Loans held for sale		987	2,448
Short-term investments			0
Cash and short-term investments		5,613	11,923
LIABILITIES
Time deposits		5,837	3,866
Short-term borrowings		8,800	761
Long-term debt		17,598	12,518
Deposits with no stated maturity		139,008	148,714
Fair Value | Derivatives Not Designated as Hedging Instruments
ASSETS
Derivative assets		1,535	1,887
Derivative assets, Netting Adjustment		(809)	(320)
LIABILITIES
Derivative liabilities		1,590	157
Derivative liabilities, Netting Adjustment		(1,910)	(1,526)
Fair Value | Derivatives Designated as Hedging Instruments
ASSETS
Derivative assets		66	75
Derivative assets, Netting Adjustment		89	36
LIABILITIES
Derivative liabilities		10	4
Derivative liabilities, Netting Adjustment		(15)	0
Fair Value | Level 1
ASSETS
Trading account assets		2	0
Other investments		3	24
Loans, net of unearned income (residential)		0	0
Loans held for sale		0	0
Securities available for sale		0	0
Held to maturity securities		0	0
Loans, net of unearned income		0	0
Loans held for sale		0	0
Short-term investments			0
Cash and short-term investments		5,613	11,923
LIABILITIES
Time deposits		0	0
Short-term borrowings		143	75
Long-term debt		10,960	11,813
Deposits with no stated maturity		0	0
Fair Value | Level 1 | Derivatives Not Designated as Hedging Instruments
ASSETS
Derivative assets		181	71
LIABILITIES
Derivative liabilities		172	66
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		1,066	701
Other investments		0	0
Loans, net of unearned income (residential)		0	0
Loans held for sale		61	281
Securities available for sale		40,000	45,364
Held to maturity securities		7,596	7,665
Loans, net of unearned income		0	0
Loans held for sale		0	0
Short-term investments			0
Cash and short-term investments		0	0
LIABILITIES
Time deposits		5,837	3,866
Short-term borrowings		8,657	686
Long-term debt		6,638	705
Deposits with no stated maturity		139,008	148,714
Fair Value | Level 2 | Derivatives Not Designated as Hedging Instruments
ASSETS
Derivative assets		2,171	2,096
LIABILITIES
Derivative liabilities		3,321	1,610
Fair Value | Level 2 | Derivatives Designated as Hedging Instruments
ASSETS
Derivative assets		(23)	39
LIABILITIES
Derivative liabilities		25	4
Fair Value | Level 3
ASSETS
Trading account assets		0	0
Other investments		1,199	543
Loans, net of unearned income (residential)		9	11
Loans held for sale		0	0
Securities available for sale		0	0
Held to maturity securities		0	0
Loans, net of unearned income		109,738	100,428
Loans held for sale		987	2,448
Short-term investments			0
Cash and short-term investments		0	0
LIABILITIES
Time deposits		0	0
Short-term borrowings		0	0
Long-term debt		0	0
Deposits with no stated maturity		0	0
Fair Value | Level 3 | Derivatives Not Designated as Hedging Instruments
ASSETS
Derivative assets		(8)	40
LIABILITIES
Derivative liabilities		7	7
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		$ 70	$ 72

[1] Total loans held for sale include real estate — residential mortgage loans held for sale at fair value of $61 million at September 30, 2022, and $281 million at December 31, 2021.