Maturity date of mortgage loan within investment in mortgage loan on real estate by entity with substantial portion of business acquiring and holding investment real estate or interest in real estate, in CCYY-MM-DD format.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 12
-Paragraph Column C
-Subsection 29

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 948
-SubTopic 310
-Section S99
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Interest rate of mortgage loan within investment in mortgage loan on real estate by entity with substantial portion of business acquiring and holding investment real estate or interest in real estate.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 12
-Paragraph Column B
-Subsection 29

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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- Definition

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

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 825
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This item represents the gross profit realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities.

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This item represents the gross loss realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities.

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Amount, before tax, of other-than-temporary impairment (OTTI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), recognized in other comprehensive income (OCI).

+ References

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-Topic 220
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Amount of cash inflow from sale of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of deferred fees paid by borrowers and unamortized costs incurred to originate loans and leases, unamortized loan commitments and loan syndication fees, and premiums over or discounts from face amounts of loans that are being amortized into income as an adjustment to yield. Excludes amounts for loans and leases covered under loss sharing agreements.

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Investments (Narratives) (Details) - USD ($) $ in Millions	12 Months Ended
Investments (Narratives) (Details) - USD ($) $ in Millions	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Assets held by insurance regulators				$ 30.8	$ 32.4
Fair value of sold available-for-sale securities	$ 114.8	$ 163.7	$ 190.2
Available-for-sale securities, gross realized gains	2.0	5.4	5.1
Available-for-sale securities, gross realized losses	0.2	0.3	2.2
Other-than-temporary impairments	0.0	0.0	$ 0.0
Mortgages [Member]
Real Estate [Abstract]
Allowance for probable losses and any unamortized premiums or discounts	$ 0.5	$ 0.5
Mortgages [Member] \| Minimum [Member]
Real Estate [Abstract]
Mortgage loan interest rate	4.10%
Mortgage loan maturity date	Jan. 01, 2019
Mortgages [Member] \| Maximum [Member]
Real Estate [Abstract]
Mortgage loan interest rate	8.20%
Mortgage loan maturity date	Dec. 31, 2036