Business Segment Information - Additional Information (Detail) - Segment	12 Months Ended
	Sep. 28, 2018	Sep. 29, 2017	Sep. 30, 2016
Segment Reporting Information [Line Items]
Number of reporting segments	3
U.S. Government
Segment Reporting Information [Line Items]
Sales as a percentage of segment sales	6.00%	3.50%	3.10%
Advanced Materials | Operating Segments | U.S. Government
Segment Reporting Information [Line Items]
Sales as a percentage of segment sales	14.70%	9.60%	9.80%
Avionics & Controls | Operating Segments | U.S. Government
Segment Reporting Information [Line Items]
Sales as a percentage of segment sales	7.10%	3.00%	2.00%