Fair Value Measurements - Carrying Amounts and Estimated Fair Values for Certain Financial Instruments (Details) - USD ($) $ in Millions		Mar. 31, 2025	Dec. 31, 2024
Financial assets:
Other short-term investments	[1]	$ 14,965	$ 17,120
Held-to-maturity securities		11,185	11,278
Loans held for sale		473	640
Portfolio loans and leases		119,807	117,439
Financial liabilities:
Deposits		165,505	167,252
Federal funds purchased		227	204
Other short-term borrowings		5,457	4,450
Long-term debt	[1]	14,539	14,337
Net Carrying Amount
Financial assets:
Cash and due from banks		3,009	3,014
Other short-term investments		14,965	17,120
Other securities		824	778
Held-to-maturity securities		11,185	11,278
Loans held for sale		28	66
Portfolio loans and leases		119,698	117,331
Financial liabilities:
Deposits		165,505	167,252
Federal funds purchased		227	204
Other short-term borrowings		5,457	4,450
Long-term debt		14,574	14,440
Net Carrying Amount | Commercial
Financial assets:
Portfolio loans and leases		73,896	72,139
Net Carrying Amount | Consumer
Financial assets:
Portfolio loans and leases		45,802	45,192
Total Fair Value
Financial assets:
Cash and due from banks		3,009	3,014
Other short-term investments		14,965	17,120
Other securities		824	778
Held-to-maturity securities		11,072	10,965
Loans held for sale		28	66
Portfolio loans and leases		117,590	114,474
Financial liabilities:
Deposits		165,617	167,353
Federal funds purchased		227	204
Other short-term borrowings		5,463	4,459
Long-term debt		14,828	14,588
Total Fair Value | Commercial
Financial assets:
Portfolio loans and leases		74,303	72,319
Total Fair Value | Consumer
Financial assets:
Portfolio loans and leases		43,288	42,155
Total Fair Value | Level 1
Financial assets:
Cash and due from banks		3,009	3,014
Other short-term investments		14,965	17,120
Other securities		0	0
Held-to-maturity securities		2,387	2,344
Loans held for sale		0	0
Portfolio loans and leases		0	0
Financial liabilities:
Deposits		0	0
Federal funds purchased		227	204
Other short-term borrowings		0	0
Long-term debt		8,667	3,753
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		824	778
Held-to-maturity securities		8,683	8,619
Loans held for sale		0	0
Portfolio loans and leases		0	0
Financial liabilities:
Deposits		165,617	167,353
Federal funds purchased		0	0
Other short-term borrowings		5,463	4,459
Long-term debt		6,161	10,835
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		28	66
Portfolio loans and leases		117,590	114,474
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		74,303	72,319
Total Fair Value | Level 3 | Consumer
Financial assets:
Portfolio loans and leases		$ 43,288	$ 42,155

[1] Includes $47 and $51 of other short-term investments, $874 and $1,000 of portfolio loans and leases, $(16) and $(19) of ALLL, $6 and $5 of other assets, $12 and $12 of other liabilities and $774 and $889 of long-term debt from consolidated VIEs that are included in their respective captions above at March 31, 2025 and December 31, 2024, respectively. For further information, refer to Note 7.