Discontinued Operations Income (Loss) Net of Tax (Detail) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Mar. 30, 2018	Mar. 31, 2017	Mar. 31, 2017	Mar. 30, 2018	Mar. 31, 2017
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Net Sales	$ 0		$ 2,268	$ 0	$ 4,964
Operating earnings (loss)	(388)		(808)	(657)	(6,735)
Tax expense (benefit)	(311)		(774)	(414)	(1,365)
Income (loss) from discontinued operations	(77)	$ (34)	(34)	(243)	(5,370)
Included in Operating Earnings (Loss):
Gain (loss) on net assets held for sale	1,306		319	1,395	(4,409)
Gain on sale of discontinued operations			1,188	0	1,188
Avionics & Controls
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Net Sales	0		2,268	0	4,964
Operating earnings (loss)	869		752	883	(119)
Tax expense (benefit)	10		(191)	33	(430)
Income (loss) from discontinued operations	859		943	850	311
Included in Operating Earnings (Loss):
Gain (loss) on net assets held for sale	801		54	750	(86)
Gain on sale of discontinued operations			1,188		1,188
Sensors & Systems
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Net Sales	0		0	0	0
Operating earnings (loss)	0		(2)	0	893
Tax expense (benefit)	0		0	0	0
Income (loss) from discontinued operations	0		(2)	0	893
Included in Operating Earnings (Loss):
Gain (loss) on net assets held for sale	0		0	0	0
Gain on sale of discontinued operations			0		0
Advanced Materials
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Net Sales	0		0	0	0
Operating earnings (loss)	(1,207)		(1,269)	(1,490)	(6,616)
Tax expense (benefit)	(308)		(482)	(434)	(623)
Income (loss) from discontinued operations	(899)		(787)	(1,056)	(5,993)
Included in Operating Earnings (Loss):
Gain (loss) on net assets held for sale	505		265	645	(4,323)
Gain on sale of discontinued operations			0		0
Other
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Net Sales	0		0	0	0
Operating earnings (loss)	(50)		(289)	(50)	(893)
Tax expense (benefit)	(13)		(101)	(13)	(312)
Income (loss) from discontinued operations	(37)		(188)	(37)	(581)
Included in Operating Earnings (Loss):
Gain (loss) on net assets held for sale	$ 0		0	$ 0	0
Gain on sale of discontinued operations			$ 0		$ 0