Carrying amount of cash and investment securities on deposit with state regulatory authorities in connection with capital requirements.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 825
-Name Accounting Standards Codification
-Section 50
-Paragraph 1A
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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 9
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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-13

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 220
-Name Accounting Standards Codification
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Investments (Narratives) (Details) - USD ($) $ in Millions	6 Months Ended
Investments (Narratives) (Details) - USD ($) $ in Millions	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