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Marketable Securities and Fair Value Measurements - Additional Information (Detail) - USD ($)
3 Months Ended 6 Months Ended
Mar. 31, 2022
Mar. 31, 2021
Mar. 31, 2022
Mar. 31, 2021
Marketable Securities [Line Items]        
Net unrealized gains (losses) $ 1,598,000 $ 596,000 $ 1,531,000 $ 2,503,000