Fair Value Measurements - Carrying Amounts and Estimated Fair Values for Certain Financial Instruments (Details) - USD ($) $ in Millions		Sep. 30, 2023	Dec. 31, 2022
Financial assets:
Other short-term investments	[1]	$ 18,923	$ 8,351
Held-to-maturity securities	[2]	2	5
Loans and leases held for sale	[3]	614	1,007
Total portfolio loans and leases, net		117,748	119,286
Financial liabilities:
Deposits		167,672	163,690
Federal funds purchased		205	180
Other short-term borrowings		4,594	4,838
Long-term debt	[1]	16,310	13,714
Net Carrying Amount
Financial assets:
Cash and due from banks		2,837	3,466
Other short-term investments		18,923	8,351
Other securities		777	874
Held-to-maturity securities		2	5
Loans and leases held for sale		117	407
Total portfolio loans and leases, net		117,635	119,163
Financial liabilities:
Deposits		167,672	163,690
Federal funds purchased		205	180
Other short-term borrowings		4,594	4,838
Long-term debt		16,562	13,778
Net Carrying Amount | Commercial
Financial assets:
Total portfolio loans and leases, net		73,931	75,262
Net Carrying Amount | Consumer
Financial assets:
Total portfolio loans and leases, net		43,704	43,901
Total Fair Value
Financial assets:
Cash and due from banks		2,837	3,466
Other short-term investments		18,923	8,351
Other securities		777	874
Held-to-maturity securities		2	5
Loans and leases held for sale		117	414
Total portfolio loans and leases, net		113,359	117,297
Financial liabilities:
Deposits		167,610	163,634
Federal funds purchased		205	180
Other short-term borrowings		4,600	4,829
Long-term debt		15,942	13,629
Total Fair Value | Commercial
Financial assets:
Total portfolio loans and leases, net		73,820	75,104
Total Fair Value | Consumer
Financial assets:
Total portfolio loans and leases, net		39,539	42,193
Total Fair Value | Level 1
Financial assets:
Cash and due from banks		2,837	3,466
Other short-term investments		18,923	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		205	180
Other short-term borrowings		0	0
Long-term debt		14,038	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 and due from banks		0	0
Other short-term investments		0	0
Other securities		777	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		167,610	163,634
Federal funds purchased		0	0
Other short-term borrowings		4,600	4,829
Long-term debt		1,904	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 and due from banks		0	0
Other short-term investments		0	0
Other securities		0	0
Held-to-maturity securities		2	5
Loans and leases held for sale		117	414
Total portfolio loans and leases, net		113,359	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		73,820	75,104
Total Fair Value | Level 3 | Consumer
Financial assets:
Total portfolio loans and leases, net		$ 39,539	$ 42,193

[1] Includes $59 and $17 of other short-term investments, $1,728 and $185 of portfolio loans and leases, $(27) and $(2) of ALLL, $11 and $2 of other assets, $15 and $9 of other liabilities, and $1,553 and $118 of long-term debt from consolidated VIEs that are included in their respective captions above at September 30, 2023 and December 31, 2022, respectively. For further information, refer to Note 12.

[2] Fair value of $2 and $5 at September 30, 2023 and December 31, 2022, respectively.

[3] Includes $497 and $600 of residential mortgage loans held for sale measured at fair value at September 30, 2023 and December 31, 2022, respectively.