Parent Company Financial Statements - Condensed Balance Sheet - Parent Company Only (Details) - USD ($) $ in Millions		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Assets
Cash		$ 3,147	$ 3,278	$ 2,681	$ 2,514
Equity securities		313	564
Goodwill		4,258	4,252	2,478
Other assets	[1]	10,749	9,190
Total Assets		204,680	169,369
Liabilities
Other short-term borrowings		1,192	1,011
Accrued expenses and other liabilities	[1]	3,409	2,422
Long-term debt (external)	[1]	14,973	14,970
Total Liabilities		181,569	148,166
Equity
Common stock	[2]	2,051	2,051
Preferred stock	[3]	2,116	1,770
Capital surplus		3,635	3,599
Retained earnings		18,384	18,315
Accumulated other comprehensive income		2,601	1,192
Treasury stock	[2]	(5,676)	(5,724)
Total Equity		23,111	21,203	16,250	16,220
Total Liabilities and Equity		204,680	169,369
Parent Company
Assets
Cash		120	118	$ 120	$ 80
Other short-term investments		5,578	4,723
Equity securities		49	49
Loans to nonbank subsidiaries		350	444
Investment in nonbank subsidiaries		25,214	23,779
Goodwill		80	80
Other assets		479	379
Total Assets		31,870	29,572
Liabilities
Other short-term borrowings		450	359
Accrued expenses and other liabilities		548	497
Long-term debt (external)		7,761	7,513
Total Liabilities		8,759	8,369
Equity
Common stock		2,051	2,051
Preferred stock		2,116	1,770
Capital surplus		3,635	3,599
Retained earnings		18,384	18,315
Accumulated other comprehensive income		2,601	1,192
Treasury stock		(5,676)	(5,724)
Total Equity		23,111	21,203
Total Liabilities and Equity		$ 31,870	$ 29,572

[1] Includes $55 and $74 of other short-term investments, $756 and $1,354 of portfolio loans and leases, $(7) and $(7) of ALLL, $5 and $8 of other assets, $2 and $2 of other liabilities and $656 and $1,253 of long-term debt from consolidated VIEs that are included in their respective captions above at December 31, 2020 and 2019, respectively. For further information, refer to Note 13.

[2] Common shares: Stated value $2.22 per share; authorized 2,000,000,000; outstanding at December 31, 2020 – 712,760,325 (excludes 211,132,256 treasury shares), 2019 – 708,915,629 (excludes 214,976,952 treasury shares).

[3] 500,000 shares of no par value preferred stock were authorized at both December 31, 2020 and 2019. There were 422,000 and 436,000 unissued shares of undesignated no par value preferred stock at December 31, 2020 and 2019, respectively. Each issued share of no par value preferred stock has a liquidation preference of $25,000. 500,000 shares of no par value Class B preferred stock were authorized at both December 31, 2020 and 2019. There were 300,000 unissued shares of undesignated no par value Class B preferred stock at both December 31, 2020 and 2019. Each issued share of no par value Class B preferred stock has a liquidation preference of $1,000.