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Reserve For Unfunded Credit Commitments.

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Stock Received In Initial Public Offering Shares.

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Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

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Commitments, Contingent Liabilities and Guarantees - Additional Information (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2026	Feb. 01, 2026	Dec. 31, 2025	Sep. 30, 2025	Mar. 31, 2025	Dec. 31, 2024	Dec. 31, 2008
Loss Contingencies
Margin account balance held by the brokerage clearing agent	$ 17		$ 13
Derivative Liabilities	3,501		2,034
Total Return Swap
Loss Contingencies
Derivative Liabilities	82		124
Comerica Incorporated \| Total Return Swap
Loss Contingencies
Business Combination, Recognized Liability Assumed, Financial Liability		$ 6
Visa
Loss Contingencies
Visa IPO, shares of Visa's Class B common stock received (in shares)							10.1
Visa Class B shares carryover basis							$ 0
Escrow deposit	125		500	$ 500	$ 375	$ 8,115	$ 3,000
Residential mortgage loans
Loss Contingencies
Fair value of liability	6
Repurchase demand request	9
Outstanding repurchase demand inventory	7		5
Swap
Loss Contingencies
Derivative Liabilities	82				$ 173
Secured Debt
Loss Contingencies
Fully and unconditionally guaranteed certain long-term borrowing obligations issued by wholly-owned issuing trust entities	62		62
Standby Letters of Credit
Loss Contingencies
Reserve for unfunded commitments	$ 20		$ 9
Standby letters of credit as a percentage of total letters of credit	99.00%		99.00%
Standby Letters of Credit \| Secured Debt
Loss Contingencies
Standby letters of credit as a percentage of total letters of credit	78.00%		77.00%
Other Liabilities
Loss Contingencies
Reserve for unfunded commitments	$ 232		$ 157
Other Liabilities \| Comerica Incorporated
Loss Contingencies
Reserve for unfunded commitments	75
Other Liabilities \| Residential mortgage loans
Loss Contingencies
Outstanding balances on residential mortgage loans sold with representation and warranty provisions	$ 4		$ 4