CONSOLIDATED STATEMENTS OF COMPREHENSIVE EARNINGS (Parenthetical) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Sep. 26, 2014	Sep. 27, 2013	Sep. 28, 2012
Statement Of Income And Comprehensive Income [Abstract]
Net gain/(loss) arising during the year, tax benefit/(expense)	$ 930	$ (1,504)	$ 1,079
Prior service cost arising during the year, tax expense	(1,240)
Amortization of prior service cost included in net periodic benefit cost, tax benefit/(expense)	(27)	159	(19)
Amortization of net actuarial loss included in net periodic benefit cost, tax expense	(529)	(608)	(548)
Increase (decrease) in unrealized gain, tax benefit/(expense)	(1,467)	(191)	(541)
Reclassification adjustments, tax benefit/(expense)	$ 479	$ 923	$ 217