Nature of Business and Summary of Significant Accounting Policies Revenue Recognition (Details) - USD ($) $ in Thousands |
12 Months Ended | |
|---|---|---|
Apr. 27, 2019 |
Apr. 28, 2018 |
|
| Organization, Consolidation and Presentation of Financial Statements [Abstract] | ||
| Precontract costs | $ 857 | $ 217 |
| Minimum | ||
| Product Warranty Liability [Line Items] | ||
| Standard parts warranty period | 1 year | |
| Installation warranty period | 1 year | |
| Maximum | ||
| Product Warranty Liability [Line Items] | ||
| Standard parts warranty period | 5 years | |
| Installation warranty period | 10 years |