Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Apr. 29, 2017	Apr. 30, 2016
Deferred tax liabilities:
Accelerated tax depreciation	$ 2.0	$ 4.1
Foreign tax withheld	4.2	2.1
Deferred income	0.4	0.8
Deferred tax liabilities	6.6	7.0
Deferred tax assets:
Deferred compensation and stock award amortization	10.1	7.9
Inventory valuation differences	2.9	2.3
Property valuation differences	1.9	2.0
Accelerated book amortization	7.2	8.9
Environmental reserves	0.5	0.7
Bad debt reserves	0.1	0.1
Vacation accruals	1.0	1.1
Foreign investment tax credit	17.9	14.4
Net operating loss carryovers	4.7	4.4
Foreign tax credits	0.0	0.9
Other accruals	2.6	3.0
Deferred tax assets, gross	48.9	45.7
Less valuation allowance	1.9	1.3
Deferred tax assets, net of valuation allowance	47.0	44.4
Net deferred tax assets	40.4	37.4
Balance sheet classification:
Current asset	0.0	11.8
Non-current asset	40.4	27.7
Current liability	$ 0.0	$ (2.1)