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Revenue - Summary of the activity for deferred revenue (Detail) - USD ($)
$ in Thousands
3 Months Ended 9 Months Ended
Jan. 27, 2019
Jan. 27, 2019
Revenue from Contract with Customer [Abstract]    
Beginning balance $ 649 $ 809 [1]
Revenue recognized on contract liabilities during the period (637) (2,171)
Payments received for services not yet rendered during the period 480 1,854
Ending balance $ 492 $ 492
[1] Derived from audited financial statements.