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Revenue - Summary of the activity for deferred revenue (Detail) - USD ($)
$ in Thousands
3 Months Ended 6 Months Ended
Oct. 28, 2018
Oct. 28, 2018
Revenue from Contract with Customer [Abstract]    
Beginning balance $ 634 $ 809 [1]
Revenue recognized on contract liabilities during the period (792) (1,534)
Payments received for services not yet rendered during the period 807 1,374
Ending balance $ 649 $ 649
[1] Derived from audited financial statements.