Intangible Assets and Goodwill - Schedule of Identifiable Intangible Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Apr. 29, 2017	Apr. 30, 2016
Acquired Finite-Lived Intangible Assets [Line Items]
Gross	$ 42.2	$ 42.2
Accumulated Amortization	35.6	33.3
Net	6.6	8.9
Customer relationships and agreements
Acquired Finite-Lived Intangible Assets [Line Items]
Gross	16.3	16.3
Accumulated Amortization	15.6	15.3
Net	$ 0.7	$ 1.0
Wtd. Avg. Remaining Amortization Periods	6 years 9 months 9 days	7 years 9 months 15 days
Trade names, patents and technology licenses
Acquired Finite-Lived Intangible Assets [Line Items]
Gross	$ 25.8	$ 25.8
Accumulated Amortization	19.9	17.9
Net	$ 5.9	$ 7.9
Wtd. Avg. Remaining Amortization Periods	1 year 5 months 9 days	2 years 4 months 21 days
Covenants not to compete
Acquired Finite-Lived Intangible Assets [Line Items]
Gross	$ 0.1	$ 0.1
Accumulated Amortization	0.1	0.1
Net	$ 0.0	$ 0.0
Wtd. Avg. Remaining Amortization Periods	5 months	1 year 5 months