Stock-Based Compensation - Expense (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Oct. 27, 2018	Oct. 28, 2017	Oct. 27, 2018	Oct. 28, 2017
Stock-based compensation expense recognized for outstanding grants
Equity-based awards expense	$ 3,639	$ 2,852	$ 5,679	$ 6,410
Liability-based awards (income) expense	(300)	(588)	(134)	308
Total stock-based compensation expense	$ 3,339	$ 2,264	$ 5,545	$ 6,718

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 14.F)
-URI http://asc.fasb.org/extlink&oid=27013229&loc=d3e301413-122809

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5047-113901

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(1)(i)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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Balance Type:	debit
Period Type:	duration