Fair Value Measurements - Carrying Amounts and Estimated Fair Values for Certain Financial Instruments (Details) - USD ($) $ in Millions		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Financial assets:
Cash		$ 2,994	$ 3,147	$ 3,278	$ 2,681
Other short-term investments	[1]	34,572	33,399
Held-to-maturity securities		8	11
Loans and leases held for sale	[2]	4,415	4,741
Total portfolio loans and leases, net		110,158	106,329
Financial liabilities:
Deposits		169,324	159,081
Federal funds purchased		281	300
Other short-term borrowings		980	1,192
Long-term debt	[1]	11,821	14,973
Net Carrying Amount
Financial assets:
Cash		2,994	3,147
Other short-term investments		34,572	33,399
Other securities		519	524
Held-to-maturity securities		8	11
Loans and leases held for sale		3,392	3,260
Total portfolio loans and leases, net		110,004	106,168
Financial liabilities:
Deposits		169,324	159,081
Federal funds purchased		281	300
Other short-term borrowings		980	1,192
Long-term debt		11,425	14,973
Net Carrying Amount | Commercial
Financial assets:
Total portfolio loans and leases, net		69,166	67,541
Net Carrying Amount | Consumer
Financial assets:
Total portfolio loans and leases, net		40,838	38,627
Total Fair Value
Financial assets:
Cash		2,994	3,147
Other short-term investments		34,572	33,399
Other securities		519	524
Held-to-maturity securities		8	11
Loans and leases held for sale		3,405	3,269
Total portfolio loans and leases, net		111,556	108,332
Financial liabilities:
Deposits		169,316	159,094
Federal funds purchased		281	300
Other short-term borrowings		980	1,192
Long-term debt		12,478	16,529
Total Fair Value | Commercial
Financial assets:
Total portfolio loans and leases, net		69,924	67,810
Total Fair Value | Consumer
Financial assets:
Total portfolio loans and leases, net		41,632	40,522
Total Fair Value | Level 1
Financial assets:
Cash		2,994	3,147
Other short-term investments		34,572	33,399
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		281	300
Other short-term borrowings		0	0
Long-term debt		12,091	15,606
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		519	524
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		169,316	159,094
Federal funds purchased		0	0
Other short-term borrowings		980	1,192
Long-term debt		387	923
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		8	11
Loans and leases held for sale		3,405	3,269
Total portfolio loans and leases, net		111,556	108,332
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		69,924	67,810
Total Fair Value | Level 3 | Consumer
Financial assets:
Total portfolio loans and leases, net		$ 41,632	$ 40,522

[1] Includes $24 and $55 of other short-term investments, $322 and $756 of portfolio loans and leases, $(2) and $(7) of ALLL, $2 and $5 of other assets, $1 and $2 of other liabilities and $263 and $656 of long-term debt from consolidated VIEs that are included in their respective captions above at December 31, 2021 and 2020, respectively. For further information, refer to Note 12.

[2] Includes $1,023 and $1,481 of residential mortgage loans held for sale measured at fair value at December 31, 2021 and 2020, respectively.