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Concentration of Credit Risk - Additional Information (Detail) - Credit Concentration Risk [Member] $ in Millions	Dec. 31, 2019 USD ($)
Corporate Bonds [Member]
Concentration Risk [Line Items]
Fair value of financial instruments	$ 154.1
Mortgage Backed Securities [Member]
Concentration Risk [Line Items]
Fair value of financial instruments	66.5
Money Market Funds [Member]
Concentration Risk [Line Items]
Fair value of financial instruments	64.6
U.S. Government Agency Securities [Member]
Concentration Risk [Line Items]
Fair value of financial instruments	36.2
U.S. Treasuries [Member]
Concentration Risk [Line Items]
Fair value of financial instruments	21.4
Asset Backed Securities [Member]
Concentration Risk [Line Items]
Fair value of financial instruments	$ 14.3

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- Definition

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

+ References

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X

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Details

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X

- Details

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- Details

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- Details

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- Details

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- Details

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