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Summary of Business and Significant Accounting Policies - Activity Related to Allowance for Doubtful Accounts (Detail) - USD ($)
$ in Thousands
12 Months Ended
Jan. 31, 2017
Jan. 31, 2016
Jan. 31, 2015
Receivables [Abstract]      
Balance at beginning of period $ 542 $ 413 $ 305
Add: charges to costs and expenses 130 201 227
Less: (write-offs) (13) (72) (119)
Balance at end of period $ 659 $ 542 $ 413