Stockholders' Equity and Stock Compensation Plans (Details 4) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Sep. 27, 2015	Sep. 28, 2014	Sep. 29, 2013
ESPP
Stock-based compensation expense	$ 10,926	$ 10,374	$ 8,775
ESPP
Stockholder's equity and stock compensation plans
Shares purchased	243	245	253
Weighted-average purchase price (in dollars per share)	$ 21.44	$ 22.99	$ 21.96
Cash received from exercise of purchase rights	$ 5,204	$ 5,604	$ 5,551
Aggregate intrinsic value	$ 1,277	$ 1,221	$ 1,140
Assumptions used in the Black-Scholes option-pricing model
Dividend yield (as a percent)	1.10%
Expected stock price volatility (as a percent)	23.70%	29.20%	27.10%
Risk-free rate of return, annual (as a percent)	0.20%	0.10%	0.10%
Expected life	1 year	1 year	1 year
ESPP
Stock-based compensation expense	$ 600	$ 700	$ 800
Unrecognized compensation cost	100	$ 200
Accumulated amount by participants to purchase the entity's common stock	$ 2,600