Investments - Additional Information (Details) $ in Millions	12 Months Ended
Dec. 31, 2021 USD ($) security	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Investments, Debt and Equity Securities [Abstract]
Gross unrealized losses (less than in 2020)	$ (5.5)	$ 0.0
Number of debt securities held, unrealized loss position \| security	259
Debt securities, available-for-sale	$ 691.4	6.6
Realized investment gains	$ 0.0	$ 0.0	$ 0.0

Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on 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 investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Number of investments in debt securities measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in unrealized loss position, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

+ References

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Amount of realized gain (loss) on investment.

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-Name Accounting Standards Codification
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