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Activity of Allowance for doubtful Accounts (Detail) - USD ($)
$ in Thousands
12 Months Ended
Jan. 31, 2017
Jan. 31, 2016
Jan. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Balance at beginning of year $ 664 $ 850 $ 1,711
Additions 4,892 6,578 4,666
Deductions (4,968) (6,764) (5,527)
Balance at end of year $ 588 $ 664 $ 850