Summary of Marketable Securities (Detail) - USD ($) $ in Thousands		Apr. 30, 2016	Apr. 30, 2015
Schedule Of Marketable Securities [Line Items]
Trading		$ 141,430	$ 131,399	[1],[2]
Less: current portion of marketable securities	[1],[2]	(11,338)	(12,580)
Non-current marketable securities	[1],[2]	130,092	118,819
Available-for-Sale		0	13,177	[1]
Less: current portion of marketable securities	[1]		(13,177)
Non-current marketable securities	[1]	0	0
Total			144,576
Less: current portion of marketable securities		(11,338)	(25,757)
Non-current marketable securities		130,092	118,819
Mutual Funds
Schedule Of Marketable Securities [Line Items]
Trading	[1],[2]	141,430	131,399
Total		$ 141,430	131,399
Corporate Bonds
Schedule Of Marketable Securities [Line Items]
Available-for-Sale	[1]		13,177
Total			$ 13,177

[1] The Company's financial assets measured at fair value on a recurring basis include trading securities classified as Level 1 and available-for-sale securities classified as Level 2. As of April 30, 2016 and 2015, the Company had no investments classified as Level 3.

[2] These investments are held in trust for settlement of the Company's vested and unvested obligations of $138.8 million and $129.1 million as of April 30, 2016 and 2015, respectively, under the ECAP (see Note 6 - Deferred Compensation and Retirement Plans). During fiscal 2016, the fair value of investments decreased; therefore, the Company recognized a loss of $3.3 million, which was recorded in other income (loss), net. During fiscal 2015 and 2014, the fair value of the investments increased; therefore, the Company recognized income of $8.8 million and $9.5 million, respectively, which was recorded in other income (loss), net.