Fair Value Measurements - Carrying Amounts and Estimated Fair Values for Certain Financial Instruments (Details) - USD ($) $ in Millions		Jun. 30, 2024	Dec. 31, 2023
Financial assets:
Other short-term investments	[1]	$ 21,085	$ 22,082
Held-to-maturity securities		11,443	2
Loans and leases held for sale (includes $512 and $334 of residential mortgage loans measured at fair value)		537	378
Portfolio loans and leases		114,291	114,912
Financial liabilities:
Deposits		166,768	168,912
Federal funds purchased		194	193
Other short-term borrowings		3,370	2,861
Long-term debt	[1]	16,293	16,380
Net Carrying Amount
Financial assets:
Cash and due from banks		2,837	3,142
Other short-term investments		21,085	22,082
Other securities		794	722
Held-to-maturity securities		11,443	2
Loans and leases held for sale (includes $512 and $334 of residential mortgage loans measured at fair value)		25	44
Portfolio loans and leases		114,182	114,796
Financial liabilities:
Deposits		166,768	168,912
Federal funds purchased		194	193
Other short-term borrowings		3,370	2,861
Long-term debt		16,445	16,418
Net Carrying Amount | Commercial
Financial assets:
Portfolio loans and leases		70,670	71,616
Net Carrying Amount | Consumer
Financial assets:
Portfolio loans and leases		43,512	43,180
Total Fair Value
Financial assets:
Cash and due from banks		2,837	3,142
Other short-term investments		21,085	22,082
Other securities		794	722
Held-to-maturity securities		11,187	2
Loans and leases held for sale (includes $512 and $334 of residential mortgage loans measured at fair value)		25	44
Portfolio loans and leases		111,393	113,176
Financial liabilities:
Deposits		166,709	168,873
Federal funds purchased		194	193
Other short-term borrowings		3,376	2,872
Long-term debt		16,363	16,384
Total Fair Value | Commercial
Financial assets:
Portfolio loans and leases		70,953	71,766
Total Fair Value | Consumer
Financial assets:
Portfolio loans and leases		40,440	41,410
Total Fair Value | Level 1
Financial assets:
Cash and due from banks		2,837	3,142
Other short-term investments		21,085	22,082
Other securities		0	0
Held-to-maturity securities		2,299	0
Loans and leases held for sale (includes $512 and $334 of residential mortgage loans measured at fair value)		0	0
Portfolio loans and leases		0	0
Financial liabilities:
Deposits		0	0
Federal funds purchased		194	193
Other short-term borrowings		0	0
Long-term debt		12,926	14,481
Total Fair Value | Level 1 | Commercial
Financial assets:
Portfolio loans and leases		0	0
Total Fair Value | Level 1 | Consumer
Financial assets:
Portfolio loans and leases		0	0
Total Fair Value | Level 2
Financial assets:
Cash and due from banks		0	0
Other short-term investments		0	0
Other securities		794	722
Held-to-maturity securities		8,886	0
Loans and leases held for sale (includes $512 and $334 of residential mortgage loans measured at fair value)		0	0
Portfolio loans and leases		0	0
Financial liabilities:
Deposits		166,709	168,873
Federal funds purchased		0	0
Other short-term borrowings		3,376	2,872
Long-term debt		3,437	1,903
Total Fair Value | Level 2 | Commercial
Financial assets:
Portfolio loans and leases		0	0
Total Fair Value | Level 2 | Consumer
Financial assets:
Portfolio loans and leases		0	0
Total Fair Value | Level 3
Financial assets:
Cash and due from banks		0	0
Other short-term investments		0	0
Other securities		0	0
Held-to-maturity securities		2	2
Loans and leases held for sale (includes $512 and $334 of residential mortgage loans measured at fair value)		25	44
Portfolio loans and leases		111,393	113,176
Financial liabilities:
Deposits		0	0
Federal funds purchased		0	0
Other short-term borrowings		0	0
Long-term debt		0	0
Total Fair Value | Level 3 | Commercial
Financial assets:
Portfolio loans and leases		70,953	71,766
Total Fair Value | Level 3 | Consumer
Financial assets:
Portfolio loans and leases		$ 40,440	$ 41,410

[1] Includes $52 and $55 of other short-term investments, $1,272 and $1,573 of portfolio loans and leases, $(23) and $(28) of ALLL, $7 and $10 of other assets, $13 and $14 of other liabilities and $1,136 and $1,409 of long-term debt from consolidated VIEs that are included in their respective captions above at June 30, 2024 and December 31, 2023, respectively. For further information, refer to Note 11.