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Regulatory Requirements and Subsidiary Dividend Restrictions - Customer Reserve Requirements (Details) - USD ($) $ in Millions | Oct. 02, 2020 | Sep. 30, 2020
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Customer Reserve Requirement [Member] |  |
Capital and Other Regulatory Requirements [Line Items] |  |
Cash reserve deposit required |  | $ 18.5
Customer SRBA [Member] |  |
Capital and Other Regulatory Requirements [Line Items] |  |
Cash reserve deposit required |  | 17.3
Customer SRBA [Member] | Subsequent Event [Member] |  |
Capital and Other Regulatory Requirements [Line Items] |  |
Cash reserve deposit required and made | $ 6.2 |
PAB Reserve Requirement [Member] |  |
Capital and Other Regulatory Requirements [Line Items] |  |
Cash reserve deposit required |  | 2.2
PAB SRBA [Member] |  |
Capital and Other Regulatory Requirements [Line Items] |  |
Cash reserve deposit required |  | $ 2.1
PAB SRBA [Member] | Subsequent Event [Member] |  |
Capital and Other Regulatory Requirements [Line Items] |  |
Cash reserve deposit required and made | $ 1.1 |

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- Definition Capital and Other Regulatory Requirements [Line Items] + References No definition available. + Details
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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 -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=116631393&loc=SL116631396-227033 + Details
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