Organization and Summary of Significant Accounting Policies - Schedule of Cash, Cash Equivalents and Restricted Cash (Detail) - USD ($) $ in Thousands	Jul. 31, 2018	Jan. 31, 2018	Jul. 31, 2017	Jan. 31, 2017
Cash And Cash Equivalents [Abstract]
Cash and cash equivalents	$ 295,289	$ 346,672	$ 309,738	$ 322,872
Restricted cash	9	9	9	8
Total as presented in the consolidated statements of cash flows	$ 295,298	$ 346,681	$ 309,747	$ 322,880