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Regulatory Requirements and Subsidiary Dividend Restrictions - Customer Reserve Requirements - Narrative (Details) - USD ($) $ in Millions | Oct. 02, 2025 | Sep. 30, 2025
--- | --- | ---
Capital and Other Regulatory Requirements [Line Items] |  |
Cash reserve deposit required |  | $ 149.0
Customer SRBA |  |
Capital and Other Regulatory Requirements [Line Items] |  |
Cash reserve deposit required |  | 147.5
Customer SRBA | Subsequent Event |  |
Capital and Other Regulatory Requirements [Line Items] |  |
Cash reserve deposit made | $ 17.2 |
PAB |  |
Capital and Other Regulatory Requirements [Line Items] |  |
Cash reserve deposit required |  | 8.9
PAB Reserve Requirement |  |
Capital and Other Regulatory Requirements [Line Items] |  |
Cash reserve deposit required |  | 8.9
PAB SRBA |  |
Capital and Other Regulatory Requirements [Line Items] |  |
Cash reserve deposit required |  | $ 14.5
PAB SRBA | Subsequent Event |  |
Capital and Other Regulatory Requirements [Line Items] |  |
Cash reserve withdrawal | $ 0.6 |

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- Definition Cash deposited in a special reserve account for the exclusive benefit of customers pursuant to SEC Regulations. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name Accounting Standards Codification -Section 50 -Paragraph 1 -SubTopic 210 -Topic 942 -Publisher FASB -URI https://asc.fasb.org/1943274/2147478482/942-210-50-1 + Details
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