Restructuring (narrative) (detail) - USD ($)	3 Months Ended				6 Months Ended
	Oct. 01, 2016	Jul. 02, 2016	Sep. 26, 2015	Jun. 27, 2015	Oct. 01, 2016	Sep. 26, 2015
Restructuring Cost and Reserve [Line Items]
Plant Restructuring	$ 277,000	$ 1,185,000	$ 15,000	$ (81,000)	$ 1,462,000	$ (66,000)
NorthwestPlant2 [Member]
Restructuring Cost and Reserve [Line Items]
Plant Restructuring	277,000	1,185,000				10,302,000
Employee Severance [Member]
Restructuring Cost and Reserve [Line Items]
Plant Restructuring	112,000	127,000	15,000	(81,000)
Employee Severance [Member] | NorthwestPlant2 [Member]
Restructuring Cost and Reserve [Line Items]
Plant Restructuring	112,000	127,000				162,000
Other Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Plant Restructuring	451,000	1,064,000	0	0
Other Restructuring [Member] | NorthwestPlant2 [Member]
Restructuring Cost and Reserve [Line Items]
Plant Restructuring	237,000	33,000				5,075,000
Long Lived Asset Charges [Member]
Restructuring Cost and Reserve [Line Items]
Plant Restructuring	(286,000)	(6,000)	$ 0	$ 0
Long Lived Asset Charges [Member] | NorthwestPlant2 [Member]
Restructuring Cost and Reserve [Line Items]
Plant Restructuring	$ 402,000	$ 1,025,000				$ 5,065,000