Investments - Contractual Maturity (Details) - USD ($) $ in Millions	Jun. 30, 2023	Dec. 31, 2022
Amortized Cost
One year or less	$ 19.5
After one year through five years	73.9
After five years	4.6
Amortized Cost	141.8	$ 127.3
Fair Value
One year or less	19.1
After one year through five years	70.9
After five years	4.4
Fair Value	135.6	121.1
Residential mortgage-backed securities
Amortized Cost
Securities	21.7
Amortized Cost	21.7	20.4
Fair Value
Securities	20.2
Fair Value	20.1	18.9
Commercial mortgage-backed securities
Amortized Cost
Securities	7.8
Amortized Cost	7.8	6.5
Fair Value
Securities	7.1
Fair Value	7.1	5.8
Asset backed securities
Amortized Cost
Securities	14.3
Amortized Cost	14.3	14.2
Fair Value
Securities	13.9
Fair Value	$ 13.9	$ 13.7

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
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+ References

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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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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).

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

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-URI https://asc.fasb.org//1943274/2147481800/320-10-50-3

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Amount 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.

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