Operating Segments Operating Segments - Additional Information (Details) $ in Billions	12 Months Ended
Dec. 31, 2025 USD ($) Segment	Dec. 31, 2024 USD ($) Segment	Dec. 31, 2023 USD ($) Segment
Segment Reporting Information [Line Items]
Number of Reportable Segments \| Segment	2	2	2
Frost Wealth Advisors [Member]
Segment Reporting Information [Line Items]
Fair value of off-balance sheet managed and custody assets \| $	$ 51.0	$ 51.4	$ 47.2

Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 47
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482785/280-10-55-47

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 54
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482785/280-10-55-54

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 18
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-18

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