Fair Value Measurements - Carrying Amounts and Estimated Fair Values for Certain Financial Instruments (Details) - USD ($) $ in Millions		Mar. 31, 2024	Dec. 31, 2023
Financial assets:
Other short-term investments	[1]	$ 22,840	$ 22,082
Held-to-maturity securities	[2]	11,520	2
Total loans and leases held for sale	[3]	339	378
Portfolio loans and leases		114,167	114,912
Financial liabilities:
Deposits		169,587	168,912
Federal funds purchased		247	193
Other short-term borrowings		2,866	2,861
Long-term debt	[1]	15,444	16,380
Net Carrying Amount
Financial assets:
Cash and due from banks		2,796	3,142
Other short-term investments		22,840	22,082
Other securities		800	722
Held-to-maturity securities		11,520	2
Total loans and leases held for sale		32	44
Portfolio loans and leases		114,054	114,796
Financial liabilities:
Deposits		169,587	168,912
Federal funds purchased		247	193
Other short-term borrowings		2,866	2,861
Long-term debt		15,573	16,418
Net Carrying Amount | Commercial
Financial assets:
Portfolio loans and leases		70,775	71,616
Net Carrying Amount | Consumer
Financial assets:
Portfolio loans and leases		43,279	43,180
Total Fair Value
Financial assets:
Cash and due from banks		2,796	3,142
Other short-term investments		22,840	22,082
Other securities		800	722
Held-to-maturity securities		11,341	2
Total loans and leases held for sale		32	44
Portfolio loans and leases		110,989	113,176
Financial liabilities:
Deposits		169,529	168,873
Federal funds purchased		247	193
Other short-term borrowings		2,871	2,872
Long-term debt		15,516	16,384
Total Fair Value | Commercial
Financial assets:
Portfolio loans and leases		70,952	71,766
Total Fair Value | Consumer
Financial assets:
Portfolio loans and leases		40,037	41,410
Total Fair Value | Level 1
Financial assets:
Cash and due from banks		2,796	3,142
Other short-term investments		22,840	22,082
Other securities		0	0
Held-to-maturity securities		2,292	0
Total loans and leases held for sale		0	0
Portfolio loans and leases		0	0
Financial liabilities:
Deposits		0	0
Federal funds purchased		247	193
Other short-term borrowings		0	0
Long-term debt		13,077	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		800	722
Held-to-maturity securities		9,047	0
Total loans and leases held for sale		0	0
Portfolio loans and leases		0	0
Financial liabilities:
Deposits		169,529	168,873
Federal funds purchased		0	0
Other short-term borrowings		2,871	2,872
Long-term debt		2,439	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
Total loans and leases held for sale		32	44
Portfolio loans and leases		110,989	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		70,952	71,766
Total Fair Value | Level 3 | Consumer
Financial assets:
Portfolio loans and leases		$ 40,037	$ 41,410

[1] Includes $48 and $55 of other short-term investments, $1,420 and $1,573 of portfolio loans and leases, $(26) and $(28) of ALLL, $29 and $10 of other assets, $25 and $14 of other liabilities and $1,274 and $1,409 of long-term debt from consolidated VIEs that are included in their respective captions above at March 31, 2024 and December 31, 2023, respectively. For further information, refer to Note 11.

[2] Fair value of $11,341 and $2 at March 31, 2024 and December 31, 2023, respectively.

[3] Includes $307 and $334 of residential mortgage loans held for sale measured at fair value at March 31, 2024 and December 31, 2023, respectively.