Investments - Contractual Maturity (Details) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Amortized Cost
One year or less	$ 39.0
After one year through five years	102.4
After five years through ten years	32.7
After ten years	1.3
Amortized Cost	212.9	$ 208.3
Fair Value
One year or less	39.0
After one year through five years	102.5
After five years through ten years	33.4
After ten years	1.2
Fair Value	212.2	205.7
Residential mortgage-backed securities
Amortized Cost
Securities	20.9
Amortized Cost	20.9	21.5
Fair Value
Securities	19.8
Fair Value	19.8	20.0
Commercial mortgage-backed securities
Amortized Cost
Securities	7.1
Amortized Cost	7.1	7.2
Fair Value
Securities	6.8
Fair Value	6.8	6.9
Asset backed securities
Amortized Cost
Securities	9.5
Amortized Cost	9.5	11.8
Fair Value
Securities	9.5
Fair Value	$ 9.5	$ 11.8

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in sixth through tenth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

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+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
-Section 50
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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in second through fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
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-Name Accounting Standards Codification
-Section 50
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-Publisher FASB
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
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+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in next fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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-Section 50
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+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

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+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

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Amortized cost excluding accrued interest, after allowance for credit loss, of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), classified as noncurrent.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
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