Condensed Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 30, 2014	Mar. 31, 2013
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 33,233	$ 18,432
Other comprehensive income before tax:
Foreign currency translation adjustments	1,275	(342)
Available-for-sale securities:
Unrealized gain	556	1,980
Reclassification of net realized (gain)/loss to net income	(128)	17
Derivative financial instruments:
Unrealized loss	(30)	(32)
Reclassification of net realized loss/(gain) to net income	562	(162)
Amortization of net actuarial loss, prior service cost and transition asset on benefit plans	3,193	5,044
Other comprehensive income before tax	5,428	6,505
Income tax expense on net unrealized gain on investments and derivatives	343	740
Other comprehensive income, net of tax	5,085	5,765
Comprehensive income	$ 38,318	$ 24,197