Fair Value Measurements - Additional Information (Detail) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2023 USD ($)	Sep. 30, 2023 USD ($)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Proceeds from the sales and maturities of securities available-for-sale		$ 28.3
Transfers between Level 1, Level 2 and Level 3 securities	$ 0.0	0.0
Net realized gain	0.8	0.7
Net unrealized loss	3.5	1.2
Collateral deposit with bank	3.2	3.2
Credit losses on available-for-sale securities	$ 0.0	0.0
Purchases of investments		$ 77.7