Discontinued Operations Income (Loss) Net of Tax (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 29, 2018	Jun. 30, 2017	Jun. 29, 2018	Jun. 30, 2017
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Net Sales	$ 0	$ 270	$ 0	$ 5,234
Operating earnings (loss)	(2,651)	(1,195)	(3,308)	(7,930)
Tax expense (benefit)	(757)	(380)	(1,171)	(1,745)
Income (loss) from discontinued operations	(1,894)	(815)	(2,137)	(6,185)
Included in Operating Earnings (Loss):
Gain (loss) on net assets held for sale	(2,175)	872	(780)	(3,537)
Gain on sale of discontinued operations		(395)	0	793
Avionics & Controls
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Net Sales	0	0	0	4,964
Operating earnings (loss)	(1,182)	(594)	(299)	(713)
Tax expense (benefit)	(35)	(62)	(2)	(492)
Income (loss) from discontinued operations	(1,147)	(532)	(297)	(221)
Included in Operating Earnings (Loss):
Gain (loss) on net assets held for sale	(1,041)	163	(291)	77
Gain on sale of discontinued operations		(395)		793
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	0	0	893
Tax expense (benefit)	0	0	0	0
Income (loss) from discontinued operations	0	0	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	270	0	270
Operating earnings (loss)	(1,452)	(598)	(2,942)	(7,214)
Tax expense (benefit)	(722)	(318)	(1,156)	(941)
Income (loss) from discontinued operations	(730)	(280)	(1,786)	(6,273)
Included in Operating Earnings (Loss):
Gain (loss) on net assets held for sale	(1,134)	709	(489)	(3,614)
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)	(17)	(3)	(67)	(896)
Tax expense (benefit)	0	0	(13)	(312)
Income (loss) from discontinued operations	(17)	(3)	(54)	(584)
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