Fair Value Measurements - Carrying Amounts and Estimated Fair Values for Certain Financial Instruments (Details) - USD ($) $ in Millions		Dec. 31, 2023	Dec. 31, 2022
Financial assets:
Other short-term investments	[1]	$ 22,082	$ 8,351
Held-to-maturity securities	[2]	2	5
Loans and leases held for sale	[3]	378	1,007
Total portfolio loans and leases, net		114,912	119,286
Financial liabilities:
Deposits		168,912	163,690
Federal funds purchased		193	180
Other short-term borrowings		2,861	4,838
Long-term debt	[1]	16,380	13,714
Net Carrying Amount
Financial assets:
Cash		3,142	3,466
Other short-term investments		22,082	8,351
Other securities		722	874
Held-to-maturity securities		2	5
Loans and leases held for sale		44	407
Total portfolio loans and leases, net		114,796	119,163
Financial liabilities:
Deposits		168,912	163,690
Federal funds purchased		193	180
Other short-term borrowings		2,861	4,838
Long-term debt		16,418	13,778
Net Carrying Amount | Commercial
Financial assets:
Total portfolio loans and leases, net		71,616	75,262
Net Carrying Amount | Consumer
Financial assets:
Total portfolio loans and leases, net		43,180	43,901
Total Fair Value
Financial assets:
Cash		3,142	3,466
Other short-term investments		22,082	8,351
Other securities		722	874
Held-to-maturity securities		2	5
Loans and leases held for sale		44	414
Total portfolio loans and leases, net		113,176	117,297
Financial liabilities:
Deposits		168,873	163,634
Federal funds purchased		193	180
Other short-term borrowings		2,872	4,829
Long-term debt		16,384	13,629
Total Fair Value | Commercial
Financial assets:
Total portfolio loans and leases, net		71,766	75,104
Total Fair Value | Consumer
Financial assets:
Total portfolio loans and leases, net		41,410	42,193
Total Fair Value | Level 1
Financial assets:
Cash		3,142	3,466
Other short-term investments		22,082	8,351
Other securities		0	0
Held-to-maturity securities		0	0
Loans and leases held for sale		0	0
Total portfolio loans and leases, net		0	0
Financial liabilities:
Deposits		0	0
Federal funds purchased		193	180
Other short-term borrowings		0	0
Long-term debt		14,481	13,218
Total Fair Value | Level 1 | Commercial
Financial assets:
Total portfolio loans and leases, net		0	0
Total Fair Value | Level 1 | Consumer
Financial assets:
Total portfolio loans and leases, net		0	0
Total Fair Value | Level 2
Financial assets:
Cash		0	0
Other short-term investments		0	0
Other securities		722	874
Held-to-maturity securities		0	0
Loans and leases held for sale		0	0
Total portfolio loans and leases, net		0	0
Financial liabilities:
Deposits		168,873	163,634
Federal funds purchased		0	0
Other short-term borrowings		2,872	4,829
Long-term debt		1,903	411
Total Fair Value | Level 2 | Commercial
Financial assets:
Total portfolio loans and leases, net		0	0
Total Fair Value | Level 2 | Consumer
Financial assets:
Total portfolio loans and leases, net		0	0
Total Fair Value | Level 3
Financial assets:
Cash		0	0
Other short-term investments		0	0
Other securities		0	0
Held-to-maturity securities		2	5
Loans and leases held for sale		44	414
Total portfolio loans and leases, net		113,176	117,297
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:
Total portfolio loans and leases, net		71,766	75,104
Total Fair Value | Level 3     | Consumer
Financial assets:
Total portfolio loans and leases, net		$ 41,410	$ 42,193

[1] Includes $55 and $17 of other short-term investments, $1,573 and $185 of portfolio loans and leases, $(28) and $(2) of ALLL, $10 and $2 of other assets, $14 and $9 of other liabilities and $1,409 and $118 of long-term debt from consolidated VIEs that are included in their respective captions above at December 31, 2023 and 2022, respectively. For further information, refer to Note 12.

[2] Fair value of $2 and $5 at December 31, 2023 and 2022, respectively.

[3] Includes $334 and $600 of residential mortgage loans held for sale measured at fair value at December 31, 2023 and 2022, respectively.