Quarterly report pursuant to Section 13 or 15(d)

Amortized Cost and Fair Values of Marketable Securities Classified as Available-For-Sale Investments (Parenthetical) (Detail)

v3.3.1.900
Amortized Cost and Fair Values of Marketable Securities Classified as Available-For-Sale Investments (Parenthetical) (Detail) - USD ($)
Oct. 31, 2015
Apr. 30, 2015
Schedule of Available-for-sale Securities [Line Items]    
Marketable securities that have been in a continuous unrealized loss position for 12 months or more $ 0 $ 0