Organization and Summary of Significant Accounting Policies - Summary of Effect of Changes to Consolidated Balance Sheet (Detail) - USD ($) $ in Thousands	Oct. 31, 2018	Jul. 31, 2018	May 01, 2018	Apr. 30, 2018	Oct. 31, 2017	Jul. 31, 2017	Apr. 30, 2017
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Total assets	$ 2,134,467			$ 2,287,914
Total liabilities	957,870			1,068,299
Total stockholders’ equity	$ 1,176,597	$ 1,164,620		$ 1,219,615	$ 1,134,723	$ 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