Organization and Summary of Significant Accounting Policies - Summary of Effect of Changes to Consolidated Balance Sheet (Detail) - USD ($) $ in Thousands	Jan. 31, 2019	Oct. 31, 2018	Jul. 31, 2018	May 01, 2018	Apr. 30, 2018	Jan. 31, 2018	Oct. 31, 2017	Jul. 31, 2017	Apr. 30, 2017
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Total assets	$ 2,217,553				$ 2,287,914
Total liabilities	1,010,513				1,068,299
Total stockholders’ equity	$ 1,207,040	$ 1,176,597	$ 1,164,620		$ 1,219,615	$ 1,180,894	$ 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