Summary of Marketable Securities (Detail) (USD $) In Thousands, unless otherwise specified	Jan. 31, 2014		Apr. 30, 2013
Schedule Of Marketable Securities [Line Items]
Trading	$ 115,123	[1],[2]	$ 98,001	[1],[2]
Less: current portion of marketable securities	(4,310)	[1],[2]	(4,537)	[1],[2]
Non-current marketable securities	110,813	[1],[2]	93,464	[1],[2]
Available-for-Sale	14,297	[2]	43,915	[2]
Less: current portion of marketable securities	(2,027)	[2]	(15,810)	[2]
Non-current marketable securities	12,270	[2]	28,105	[2]
Total	129,420		141,916
Less: current portion of marketable securities	(6,337)		(20,347)
Non-current marketable securities	123,083		121,569
Mutual Funds
Schedule Of Marketable Securities [Line Items]
Trading	115,123	[1],[2]	98,001	[1],[2]
Total	115,123		98,001
Corporate Bonds
Schedule Of Marketable Securities [Line Items]
Available-for-Sale	14,297	[2]	42,111	[2]
Total	14,297		42,111
U.S. Treasury And Agency Securities
Schedule Of Marketable Securities [Line Items]
Available-for-Sale			1,804	[2]
Total			$ 1,804

[1] These investments are held in trust for settlement of the Company's vested and unvested obligations of $116.4 million and $99.2 million as of January 31, 2014 and April 30, 2013, respectively, under the ECAP (see Note 6 - Deferred Compensation and Retirement Plans).

[2] 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 January 31, 2014 and April 30, 2013, the Company had cash equivalents of $129.2 million and $93.6 million, respectively, classified as Level 1. As of April 30, 2013, the Company had restricted cash of $2.9 million, classified as Level 1. As of January 31, 2014, the Company had no restricted cash balance. As of January 31, 2014 and April 30, 2013, the Company had no investments classified as Level 3.