Fair Value Measurements - Carrying Amounts and Estimated Fair Values for Certain Financial Instruments (Details) - USD ($) $ in Millions		Dec. 31, 2024	Dec. 31, 2023
Financial assets:
Other short-term investments	[1]	$ 17,120	$ 22,082
Held-to-maturity securities		11,278	2
Loans and leases held for sale		640	378
Total portfolio loans and leases, net		117,439	114,912
Financial liabilities:
Deposits		167,252	168,912
Federal funds purchased		204	193
Other short-term borrowings		4,450	2,861
Long-term debt	[1]	14,337	16,380
Net Carrying Amount
Financial assets:
Cash		3,014	3,142
Other short-term investments		17,120	22,082
Other securities		778	722
Held-to-maturity securities		11,278	2
Loans and leases held for sale		66	44
Total portfolio loans and leases, net		117,331	114,796
Financial liabilities:
Deposits		167,252	168,912
Federal funds purchased		204	193
Other short-term borrowings		4,450	2,861
Long-term debt		14,440	16,418
Net Carrying Amount | Commercial
Financial assets:
Total portfolio loans and leases, net		72,139	71,616
Net Carrying Amount | Consumer
Financial assets:
Total portfolio loans and leases, net		45,192	43,180
Total Fair Value
Financial assets:
Cash		3,014	3,142
Other short-term investments		17,120	22,082
Other securities		778	722
Held-to-maturity securities		10,965	2
Loans and leases held for sale		66	44
Total portfolio loans and leases, net		114,474	113,176
Financial liabilities:
Deposits		167,353	168,873
Federal funds purchased		204	193
Other short-term borrowings		4,459	2,872
Long-term debt		14,588	16,384
Total Fair Value | Commercial
Financial assets:
Total portfolio loans and leases, net		72,319	71,766
Total Fair Value | Consumer
Financial assets:
Total portfolio loans and leases, net		42,155	41,410
Total Fair Value | Level 1
Financial assets:
Cash		3,014	3,142
Other short-term investments		17,120	22,082
Other securities		0	0
Held-to-maturity securities		2,344	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		204	193
Other short-term borrowings		0	0
Long-term debt		3,753	14,481
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		778	722
Held-to-maturity securities		8,619	0
Loans and leases held for sale		0	0
Total portfolio loans and leases, net		0	0
Financial liabilities:
Deposits		167,353	168,873
Federal funds purchased		0	0
Other short-term borrowings		4,459	2,872
Long-term debt		10,835	1,903
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	2
Loans and leases held for sale		66	44
Total portfolio loans and leases, net		114,474	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:
Total portfolio loans and leases, net		72,319	71,766
Total Fair Value | Level 3     | Consumer
Financial assets:
Total portfolio loans and leases, net		$ 42,155	$ 41,410

[1] Includes $51 and $55 of other short-term investments, $1,000 and $1,573 of portfolio loans and leases, $(19) and $(28) of ALLL, $5 and $10 of other assets, $12 and $14 of other liabilities and $889 and $1,409 of long-term debt from consolidated VIEs that are included in their respective captions above at December 31, 2024 and 2023, respectively. For further information, refer to Note 12.