Summary of Marketable Securities (Detail) - USD ($) $ in Thousands		Apr. 30, 2015	Apr. 30, 2014
Schedule Of Marketable Securities [Line Items]
Trading	[1],[2]	$ 131,399	$ 116,207
Less: current portion of marketable securities	[1],[2]	(12,580)	(4,510)
Non-current marketable securities	[1],[2]	118,819	111,697
Available-for-Sale	[1]	13,177	18,352
Less: current portion of marketable securities	[1]	(13,177)	(5,056)
Non-current marketable securities	[1]		13,296
Total		144,576	134,559
Less: current portion of marketable securities		(25,757)	(9,566)
Non-current marketable securities		118,819	124,993
Mutual Funds
Schedule Of Marketable Securities [Line Items]
Trading	[1],[2]	131,399	116,207
Total		131,399	116,207
Corporate Bonds
Schedule Of Marketable Securities [Line Items]
Available-for-Sale	[1]	13,177	18,352
Total		$ 13,177	$ 18,352

[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, 2015 and 2014, 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 $129.1 million and $117.6 million as of April 30, 2015 and 2014, respectively, under the ECAP (see Note 6 - Deferred Compensation and Retirement Plans). During fiscal 2015, 2014 and 2013, the fair value of the investments increased; therefore, the Company recognized income of $8.8 million, $9.5 million, and $7.6 million, respectively, which was recorded in other income, net.