Fair Value Measurements - Carrying Amounts and Estimated Fair Values for Certain Financial Instruments (Details) - USD ($) $ in Millions		Sep. 30, 2024	Dec. 31, 2023
Financial assets:
Other short-term investments	[1]	$ 21,729	$ 22,082
Held-to-maturity securities		11,358	2
Loans held for sale		612	378
Portfolio loans and leases		114,363	114,912
Financial liabilities:
Deposits		168,340	168,912
Federal funds purchased		169	193
Other short-term borrowings		1,424	2,861
Long-term debt	[1]	17,096	16,380
Net Carrying Amount
Financial assets:
Cash and due from banks		3,215	3,142
Other short-term investments		21,729	22,082
Other securities		777	722
Held-to-maturity securities		11,358	2
Loans held for sale		100	44
Portfolio loans and leases		114,249	114,796
Financial liabilities:
Deposits		168,340	168,912
Federal funds purchased		169	193
Other short-term borrowings		1,424	2,861
Long-term debt		17,058	16,418
Net Carrying Amount | Commercial
Financial assets:
Portfolio loans and leases		70,025	71,616
Net Carrying Amount | Consumer
Financial assets:
Portfolio loans and leases		44,224	43,180
Total Fair Value
Financial assets:
Cash and due from banks		3,215	3,142
Other short-term investments		21,729	22,082
Other securities		777	722
Held-to-maturity securities		11,554	2
Loans held for sale		100	44
Portfolio loans and leases		112,719	113,176
Financial liabilities:
Deposits		168,319	168,873
Federal funds purchased		169	193
Other short-term borrowings		1,429	2,872
Long-term debt		17,431	16,384
Total Fair Value | Commercial
Financial assets:
Portfolio loans and leases		70,529	71,766
Total Fair Value | Consumer
Financial assets:
Portfolio loans and leases		42,190	41,410
Total Fair Value | Level 1
Financial assets:
Cash and due from banks		3,215	3,142
Other short-term investments		21,729	22,082
Other securities		0	0
Held-to-maturity securities		2,379	0
Loans held for sale		0	0
Portfolio loans and leases		0	0
Financial liabilities:
Deposits		0	0
Federal funds purchased		169	193
Other short-term borrowings		0	0
Long-term debt		13,979	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		777	722
Held-to-maturity securities		9,173	0
Loans held for sale		0	0
Portfolio loans and leases		0	0
Financial liabilities:
Deposits		168,319	168,873
Federal funds purchased		0	0
Other short-term borrowings		1,429	2,872
Long-term debt		3,452	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 held for sale		100	44
Portfolio loans and leases		112,719	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		70,529	71,766
Total Fair Value | Level 3 | Consumer
Financial assets:
Portfolio loans and leases		$ 42,190	$ 41,410

[1] Includes $50 and $55 of other short-term investments, $1,131 and $1,573 of portfolio loans and leases, $(21) and $(28) of ALLL, $8 and $10 of other assets, $13 and $14 of other liabilities and $1,008 and $1,409 of long-term debt from consolidated VIEs that are included in their respective captions above at September 30, 2024 and December 31, 2023, respectively. For further information, refer to Note 12.