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Significant Accounting Policies - Narrative (Details) - USD ($) $ in Thousands | 3 Months Ended | 12 Months Ended |
--- | --- | --- | ---
Oct. 29, 2017 | Jan. 28, 2018 | Jan. 29, 2017 | Jan. 31, 2016 | Apr. 30, 2017
Aggregate net investments under cost method of accounting |  | $ 38,100 | $ 27,100 |  |
Impairment of assets | $ 4,250 | 4,250 | 0 | $ 0 |
Deferred tax assets (and increase in valuation allowance) recognized for the windfall tax benefits |  | 8,400 |  |  | $ 8,400
Cumulative effect adjustment to retained earnings from adoption of ASU 2016-09 |  | $ 2,021 |  |  |
Other Intangible Assets and Long-lived Assets [Abstract] |  |  |  |  |
Percent of realizable undiscounted cash flows used to determine useful life of acquired finite-lived intangible assets, minimum |  | 90.00% |  |  |
Sales and Marketing [Abstract] |  |  |  |  |
Advertising costs |  | $ 600 | 400 | 200 |
Product Development and Engineering [Abstract] |  |  |  |  |
Recoveries from nonrecurring engineering services |  | $ 5,400 | 11,900 | $ 21,100 |
Cash equivalents | Maximum |  |  |  |  |
Investment maturity period |  | 90 days |  |  |
Other assets |  |  |  |  |
Aggregate net investments under cost method of accounting |  | $ 28,000 |  |  |
Total equity method investments |  | 3,400 | $ 2,000 |  |
Retained Earnings |  |  |  |  |
Cumulative effect adjustment to retained earnings from adoption of ASU 2016-09 |  | 2,021 |  |  | $ 2,021
ASU 2014-09 [Member] | Minimum |  |  |  |  |
Increase in retained earnings expected from adopting the standard in fiscal 2019 |  | 10,000 |  |  |
ASU 2014-09 [Member] | Maximum |  |  |  |  |
Increase in retained earnings expected from adopting the standard in fiscal 2019 |  | $ 12,000 |  |  |

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