Quarterly report pursuant to Section 13 or 15(d)

Investments - Additional Information (Detail)

v3.8.0.1
Investments - Additional Information (Detail)
6 Months Ended
Sep. 30, 2017
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 May 15, 2018
Treasury with original maturities period 1 year