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Investments - Additional Information (Detail)
6 Months Ended
Sep. 30, 2019
Minimum [Member]  
Schedule of Held-to-maturity Securities [Line Items]  
Treasury with original maturities period 3 months
Maximum [Member]  
Schedule of Held-to-maturity Securities [Line Items]  
Investment maturity date range end Dec. 30, 2019
Treasury with original maturities period 1 year