Restructuring and Cost Management Plans - Amounts Related to Restructuring Costs Payable (Details) - USD ($) $ in Thousands		6 Months Ended				12 Months Ended
		Sep. 30, 2017		Jul. 01, 2017		Apr. 01, 2017
Restructuring Reserve [Roll Forward]
Restructuring Reserve Start		$ 4,996
Restructuring Reserve End		2,466				$ 4,996
Q4 FY17 Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost		16,475		$ 24,061		7,587
Restructuring Reserve [Roll Forward]
Restructuring Reserve Start		4,135				0
Restructuring Reserve End		1,629				4,135
Q4 FY17 Restructuring Plan [Member] | Employee Severance [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost		577		4,165		3,588
Restructuring Reserve [Roll Forward]
Restructuring Reserve Start		3,247				0
Restructuring Reserve End		152				3,247
Q4 FY17 Restructuring Plan [Member] | Current Asset Impairments and Other Gross Profit [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost		13,278	[1]	$ 14,947	[2]	1,669	[1]
Restructuring Reserve [Roll Forward]
Restructuring Reserve Start	[1]	0				0
Restructuring Reserve End	[1]	652				0
Q4 FY17 Restructuring Plan [Member] | Site Closures and Non-current Asset Impairments [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost		2,457
Chelmsford Plan [Domain]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost		356				401
Restructuring Reserve [Roll Forward]
Restructuring Reserve Start		861				757
Restructuring Reserve End		$ 837				$ 861

[1] (1) Asset and facilities costs include inventory charges recorded in cost of sales.

[2] (1) Current asset impairments include inventory charges recorded in cost of sales.