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Organization and Summary of Significant Accounting Policies - Schedule of Cash, Cash Equivalents and Restricted Cash (Detail) - USD ($)
$ in Thousands
Apr. 30, 2018
Jan. 31, 2018
Apr. 30, 2017
Jan. 31, 2017
Cash And Cash Equivalents [Abstract]        
Cash and cash equivalents $ 336,692 $ 346,672 $ 335,182 $ 322,872
Restricted cash 9 9 9 8
Total as presented in the consolidated statements of cash flows $ 336,701 $ 346,681 $ 335,191 $ 322,880