Cash Flow Information - Non-Cash Investing and Financing Activities (Details) - USD ($) $ in Thousands |
12 Months Ended | ||
|---|---|---|---|
Apr. 27, 2019 |
Apr. 28, 2018 |
Apr. 29, 2017 |
|
| Supplemental Cash Flow Elements [Abstract] | |||
| Demonstration equipment transferred to inventory | $ 97 | $ 72 | $ 218 |
| Purchases of property and equipment included in accounts payable | 1,106 | 1,983 | 2,524 |
| Contributions of common stock under the ESPP | 1,650 | 1,682 | 840 |
| Contingent consideration related to acquisition | $ 0 | $ 0 | $ 31 |