Retirement and Benefit Plans - Assumptions used in Calculating Benefit Obligation (Details) - Acquired Comerica Plans	2 Months Ended
Mar. 31, 2026
Pension Plan \| Qualified Plan
Defined Benefit Plan Disclosure [Line Items]
Discount rate	5.62%
Rate of compensation increase	4.50%
Expected long-term return on plan assets	6.75%
Pension Plan \| Qualified Plan \| Minimum
Defined Benefit Plan Disclosure [Line Items]
Interest crediting rate	4.87%
Pension Plan \| Qualified Plan \| Maximum
Defined Benefit Plan Disclosure [Line Items]
Interest crediting rate	5.25%
Pension Plan \| Nonqualified Plan
Defined Benefit Plan Disclosure [Line Items]
Discount rate	5.57%
Rate of compensation increase	4.50%
Pension Plan \| Nonqualified Plan \| Minimum
Defined Benefit Plan Disclosure [Line Items]
Interest crediting rate	4.87%
Pension Plan \| Nonqualified Plan \| Maximum
Defined Benefit Plan Disclosure [Line Items]
Interest crediting rate	5.25%
Postemployment Retirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Discount rate	5.40%
Expected long-term return on plan assets	2.50%

Weighted average rate for present value of future retirement benefits cash flows, used to determine benefit obligation of defined benefit plan.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
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-Section 50
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- Definition

Weighted average rate increase of compensation, used to determine benefit obligation of defined benefit plan. Plan includes, but is not limited to, pay-related defined benefit plan.

+ References

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- Definition

Weighted average rate of return on plan assets, reflecting average rate of earnings expected on existing plan assets and expected contributions, used to determine net periodic benefit cost of defined benefit plan.

+ References

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- Definition

Weighted-average interest crediting rate used to determine net periodic benefit cost of defined benefit plan. Plan includes, but is not limited to, cash balance and other defined benefit plans with promised interest crediting rate.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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