Summary of Quarterly Results of Operations (Unaudited) - Summary of Unaudited Quarterly Results of Operations (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	12 Months Ended
Apr. 28, 2018	Jan. 27, 2018	Oct. 28, 2017	Jul. 29, 2017	Apr. 29, 2017	Jan. 28, 2017	Oct. 29, 2016	Jul. 30, 2016	Apr. 28, 2018	Apr. 29, 2017	Apr. 30, 2016
Segment Reporting Information [Line Items]
Business Combination, Acquisition Related Costs	$ 0.0	$ 0.0	$ 4.2	$ 2.6	$ 1.5	$ 0.0	$ 0.0	$ 0.0
Revenue from Grants	(2.2)	(3.6)	(1.5)	0.0	(1.5)	(1.5)	(1.5)	0.0
Income Tax Expense									$ 66.6	$ 23.0	$ 26.3
Foreign Investment Tax Credit	(8.7)	(0.3)	(0.4)	(0.4)					(9.8)	(4.7)	(2.1)
Net Sales	249.0	228.0	230.1	201.2	219.7	195.6	209.3	191.9	908.3	816.5	809.1
Gross Profit	61.9	60.1	62.0	55.6	55.2	53.4	55.6	54.1	239.6	218.3	212.9
Net Income	$ 36.8	$ (24.3)	$ 24.2	$ 20.5	$ 23.1	$ 23.7	$ 24.9	$ 21.2	57.2	$ 92.9	$ 84.6
Net income per diluted common share (in dollars per share)	$ 0.98	$ (0.65)	$ 0.64	$ 0.55	$ 0.62	$ 0.63	$ 0.66	$ 0.57
Net income per basic common share (in dollars per share)	$ 0.99	$ (0.65)	$ 0.65	$ 0.55	$ 0.62	$ 0.64	$ 0.66	$ 0.57
Hetronic Lawsuit
Segment Reporting Information [Line Items]
Legal Fees	$ 2.1	$ 1.5	$ 1.6	$ 2.9	$ 2.8	$ 1.6	$ 2.3	$ 4.3
RSAs \| Executives and non-executive members of management \| 2014 Incentive Plan
Segment Reporting Information [Line Items]
Allocated share-based compensation expense, amount recorded to true-up prior periods	0.0	(6.0)	0.0	0.0
Total Impact of U.S. Tax Reform [Member]
Segment Reporting Information [Line Items]
Income Tax Expense	$ (3.1)	$ 56.8	$ 0.0	$ 0.0					$ 53.7

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This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities.

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The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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