Income Taxes - Effective Rate and Uncertain Tax Positions (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Jan. 27, 2018	Jan. 28, 2017	Jan. 27, 2018	Jan. 28, 2017
Income Taxes
Effective tax rate (as a percent)	62.00%	29.40%	43.90%	33.40%
Net liability for uncertain income tax positions	$ 1.1		$ 1.1

Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=65882285&loc=d3e32698-109319

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(h)(2))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=65882285&loc=d3e32687-109319

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration