Stockholders' Equity and Stock Compensation Plans (Details 4) (USD $) Share data in Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Sep. 28, 2014	Sep. 29, 2013	Sep. 30, 2012
ESPP
Stock-based compensation expense	$ 10,374,000	$ 8,775,000	$ 10,839,000
ESPP
Stockholder's equity and stock compensation plans
Shares purchased	245	253	289
Weighted-average purchase price (in dollars per share)	$ 22.99	$ 21.96	$ 18.35
Cash received from exercise of purchase rights	5,604,000	5,551,000	5,300,000
Aggregate intrinsic value	1,221,000	1,140,000	935,000
Assumptions used in the Black-Scholes option-pricing model
Expected stock price volatility (as a percent)	29.20%	27.10%	34.70%
Risk-free rate of return, annual (as a percent)	0.10%	0.10%	0.10%
Expected life	1 year	1 year	1 year
ESPP
Stock-based compensation expense	700,000	800,000	900,000
Unrecognized compensation cost	200,000	200,000
Accumulated amount by participants to purchase the entity's common stock	$ 2,900,000