Parent Company Financial Statements Parent Company Financial Statements (Balance Sheets) (Details) - USD ($) $ / shares in Units, $ in Millions		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Condensed Financial Statements, Captions [Line Items]
Cash and due from subsidiary bank		$ 1,236	$ 1,031
Other short-term investments		197	172
Premises and equipment		454	459
Accrued income and other assets		5,603	5,360
Total assets		94,616	88,129
Medium- and long-term debt		2,796	5,728
Accrued expenses and other liabilities		1,584	1,482
Total liabilities		$ 86,719	$ 80,079
Preferred Stock, No Par Value		$ 0	$ 0
Preferred Stock, Shares Authorized		4,000	4,000
Preferred Stock, Shares Issued		4,000	4,000
Fixed rate reset non-cumulative perpetual preferred stock, series A, no par value, $100,000 liquidation preference per share: Authorized - 4,000 shares, Issued - 4,000 shares at 12/31/2021 and 12/31/2020			$ 394
Common stock, par value		$ 5	$ 5
Common stock, authorized shares		325,000,000	325,000,000
Common stock, issued shares		228,164,824	228,164,824
Common stock - $5 par value: Authorized - 325,000,000 shares; Issued - 228,164,824 shares			$ 1,141
Capital surplus			2,185
Accumulated other comprehensive (loss) income		$ (212)	64	$ (316)
Retained earnings			$ 9,727
Shares in treasury		97,476,872	88,997,430
Less cost of common stock in treasury - 97,476,872 shares at 12/31/21 and 88,997,430 shares at 12/31/20			$ 5,461
Total shareholders' equity		$ 7,897	8,050	$ 7,327	$ 7,507
Total liabilities and shareholders' equity		94,616	88,129
Parent Company
Condensed Financial Statements, Captions [Line Items]
Cash and due from subsidiary bank		1,105	1,489
Other short-term investments		113	107
Due from Affiliates	[1]	150	0
Investments in subsidiaries, principally banks		8,278	8,215
Premises and equipment		1	1
Accrued income and other assets		265	329
Total assets		9,912	10,141
Medium- and long-term debt		1,736	1,818
Accrued expenses and other liabilities		279	273
Total liabilities		2,015	2,091
Fixed rate reset non-cumulative perpetual preferred stock, series A, no par value, $100,000 liquidation preference per share: Authorized - 4,000 shares, Issued - 4,000 shares at 12/31/2021 and 12/31/2020		394	394
Common stock - $5 par value: Authorized - 325,000,000 shares; Issued - 228,164,824 shares		1,141	1,141
Capital surplus		2,175	2,185
Accumulated other comprehensive (loss) income	[2]	(212)	64
Retained earnings	[2]	10,494	9,727
Less cost of common stock in treasury - 97,476,872 shares at 12/31/21 and 88,997,430 shares at 12/31/20		(6,095)	(5,461)
Total shareholders' equity		7,897	8,050
Total liabilities and shareholders' equity		$ 9,912	$ 10,141

[1] In third quarter 2021 the Corporation issued a $150 million loan to Comerica Bank that, after an initial term of 13 months, will automatically extend at the end of each month to roll into a new 13 month plus one day term.

[2] Balances for the year ended December 31, 2020 have been recast to reflect the retrospective application of the Corporation's election to change the accounting method for certain components of the qualified defined benefit pension plan as of January 1, 2021. Refer to Note 1 for further information.