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Short-term investments - Additional Information (Detail) - USD ($)
$ in Millions
3 Months Ended 9 Months Ended
Sep. 30, 2023
Sep. 30, 2023
Dec. 31, 2022
Debt Securities, Available-for-Sale [Line Items]      
Accrued interest $ 1.0 $ 1.0 $ 1.4
Interest Income [Member]      
Debt Securities, Available-for-Sale [Line Items]      
Gain (loss) in short-term investments $ 0.2 $ 0.5