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
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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Investments (Narratives) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Investments (Narratives) (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2023	Dec. 31, 2022	Mar. 31, 2023
Available-for-sale Securities [Abstract]
Available for sale securities, gross realized losses		$ 1.1	$ 0.5
Gross realized gains on sales of Treasuries		1.5	1.1
Statutory Accounting Practices, Statutory Amount Available for Dividend Payments [Abstract]
Assets Held by Insurance Regulators	$ 22.5	22.5		$ 23.4
Provision for Loan, Lease, and Other Losses [Abstract]
Financing Receivable, Credit Loss, Expense (Reversal)		0.4	$ 2.2
Matured or Redeemed Securities
Available-for-sale Securities [Abstract]
Available for sale securities, realized gains	58.5	448.9
Corporate securities [Member]
Available-for-sale Securities [Abstract]
Available for sale securities, realized gains	$ 42.1	147.6
Moving and Storage Treasuries
Available-for-sale Securities [Abstract]
Available for sale securities, realized gains		$ 225.0