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Investments (Narratives) (Details) - USD ($) $ in Millions | 6 Months Ended |
--- | --- | ---
Sep. 30, 2024 | Sep. 30, 2023 | Mar. 31, 2024
Statutory Accounting Practices, Statutory Amount Available for Dividend Payments [Abstract] |  |  |
Assets Held by Insurance Regulators | $ 20.0 |  | $ 23.1
Available-for-sale Securities [Abstract] |  |  |
Available for sale securities, gross realized losses | 0.3 | $ 1.1 |
Provision for Loan, Lease, and Other Losses [Abstract] |  |  |
Financing Receivable, Credit Loss, Expense (Reversal) | 1.8 | 0.4 |
Matured or Redeemed Securities |  |  |
Available-for-sale Securities [Abstract] |  |  |
Available for sale securities, realized gains | 200.8 | 405.2 |
Moving and Storage Treasuries |  |  |
Available-for-sale Securities [Abstract] |  |  |
Available for sale securities, realized gains | 73.0 | 225.0 |
Corporate securities [Member] |  |  |
Available-for-sale Securities [Abstract] |  |  |
Available for sale securities, realized gains | $ 2.1 | $ 1.5 |

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- Definition Carrying amount of cash and investment securities on deposit with state regulatory authorities in connection with capital requirements. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 944 -SubTopic 825 -Name Accounting Standards Codification -Section 50 -Paragraph 1A -Publisher FASB -URI https://asc.fasb.org/1943274/2147477351/944-825-50-1A + Details
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