Segment Information and Geographic Area Information - Schedule of Segment Reporting Information, by Segment (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Apr. 29, 2017	Jan. 28, 2017	Oct. 29, 2016	Jul. 30, 2016	Apr. 30, 2016	Jan. 30, 2016	Oct. 31, 2015	Aug. 01, 2015	Apr. 29, 2017	Apr. 30, 2016	May 02, 2015
Segment Reporting Information [Line Items]
Net sales									$ 816.5	$ 809.1	$ 881.1
Net sales to unaffiliated customers	$ 219.7	$ 195.6	$ 209.3	$ 191.9	$ 212.8	$ 184.6	$ 208.4	$ 203.3	816.5	809.1	881.1
Income/(loss) from operations									110.8	109.7	112.2
Gain from sale of business									0.0	0.0	(7.7)
Interest income, net									(0.4)	(0.7)	(0.7)
Other (income) expense, net									4.7	0.5	0.2
Income/(loss) before income taxes									115.9	110.9	120.8
Depreciation and amortization									24.3	23.9	23.4
Identifiable assets	704.0				655.9				704.0	655.9	605.8
Transfers between segments
Segment Reporting Information [Line Items]
Net sales									0.0	0.0	0.0
Automotive
Segment Reporting Information [Line Items]
Depreciation and amortization									15.5		16.6
Identifiable assets	462.3								462.3		365.5
Automotive | Operating Segments
Segment Reporting Information [Line Items]
Net sales									641.0	623.1	633.0
Net sales to unaffiliated customers									632.2	614.3	628.4
Income/(loss) from operations									148.3	136.8	124.9
Depreciation and amortization										15.6
Identifiable assets					418.4					418.4
Automotive | Transfers between segments
Segment Reporting Information [Line Items]
Net sales									(8.8)	(8.8)	(4.6)
Interface
Segment Reporting Information [Line Items]
Depreciation and amortization									4.2		2.8
Identifiable assets	202.5								202.5		186.4
Interface | Operating Segments
Segment Reporting Information [Line Items]
Net sales									128.2	142.6	163.8
Net sales to unaffiliated customers									127.4	140.8	161.7
Income/(loss) from operations									(0.9)	2.7	7.0
Depreciation and amortization										4.3
Identifiable assets					184.8					184.8
Interface | Transfers between segments
Segment Reporting Information [Line Items]
Net sales									(0.8)	(1.8)	(2.1)
Power Products
Segment Reporting Information [Line Items]
Depreciation and amortization									2.8		2.4
Identifiable assets	46.2								46.2		38.5
Power Products | Operating Segments
Segment Reporting Information [Line Items]
Net sales									56.5	54.1	86.1
Net sales to unaffiliated customers									56.3	53.5	85.7
Income/(loss) from operations									11.5	9.4	23.2
Depreciation and amortization										2.3
Identifiable assets					46.4					46.4
Power Products | Transfers between segments
Segment Reporting Information [Line Items]
Net sales									(0.2)	(0.6)	(0.4)
Other
Segment Reporting Information [Line Items]
Depreciation and amortization									1.0		0.4
Identifiable assets	5.2								5.2		3.7
Other | Operating Segments
Segment Reporting Information [Line Items]
Net sales									2.2	0.6	5.5
Net sales to unaffiliated customers									0.3	0.3	5.2
Income/(loss) from operations									(12.4)	(8.8)	(6.4)
Depreciation and amortization										0.6
Identifiable assets					5.0					5.0
Other | Transfers between segments
Segment Reporting Information [Line Items]
Net sales									(1.9)	(0.3)	(0.3)
Eliminations/Corporate
Segment Reporting Information [Line Items]
Net sales									(11.4)	(11.3)	(7.3)
Net sales to unaffiliated customers									0.3	0.2	0.1
Income/(loss) from operations									(35.7)	(30.4)	(36.5)
Depreciation and amortization									0.8	1.1	1.2
Identifiable assets	$ (12.2)				$ 1.3				(12.2)	1.3	11.7
Eliminations/Corporate | Transfers between segments
Segment Reporting Information [Line Items]
Net sales									$ 11.7	$ 11.5	$ 7.4