Investments - Additional Information (Detail) $ in Millions	Dec. 31, 2024 USD ($) security	Dec. 31, 2023 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Debt securities, available-for-sale, term	2 years 7 months 28 days	2 years 8 months 4 days
Number of securities in an unrealized loss position, total	1,042
Number of securities in an unrealized loss position for less than one year	105
Number of securities in an unrealized loss position for a period of one year or greater	13
Mortgage Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial mortgage loans, allowance for expected credit losses | $	$ 1.2	$ 0.2
Private Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial mortgage loans, allowance for expected credit losses | $	$ 4.4	$ 0.0