Organization and Summary of Significant Accounting Policies - Summary of Effect of Changes to Consolidated Balance Sheet (Detail) - USD ($) $ in Thousands	Jul. 31, 2018	May 01, 2018	Apr. 30, 2018	Jul. 31, 2017	Apr. 30, 2017
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Total assets	$ 2,079,470		$ 2,287,914
Total liabilities	914,850		1,068,299
Total stockholders’ equity	$ 1,164,620		$ 1,219,615	$ 1,128,751	$ 1,087,048
Accounting Standards Update 2014-09
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Total assets		$ 2,291,410
Total liabilities		1,065,139
Total stockholders’ equity		1,226,271
Adjustments Due to ASC 606 | Accounting Standards Update 2014-09
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Total assets		3,496
Total liabilities		(3,160)
Total stockholders’ equity		$ 6,656