Schedule of Changes in Outstanding Common Shares and Treasury Stock (Detail) - shares	12 Months Ended
	Sep. 29, 2017	Sep. 30, 2016
Equity [Abstract]
Shares issued, beginning of year	32,564,252	32,378,185
Shares issued under share-based compensation plans	553,221	186,067
Shares issued, end of year	33,117,473	32,564,252
Treasury stock purchased, beginning of year	(3,135,927)	(2,831,350)
Treasury stock purchased	0	(304,577)
Treasury stock purchased, end of year	(3,135,927)	(3,135,927)
Shares outstanding, end of year	29,981,546	29,428,325