Consolidated Statements of Comprehensive Income (Unaudited) (Parenthetical) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 27, 2013	Sep. 28, 2012	Sep. 27, 2013	Sep. 28, 2012
Income Statement [Abstract]
Tax on unrealized holding gain (loss) on investments arising during period	$ 30	$ 43	$ (12)	$ 108
Tax on reclassification adjustments for gain on investments included in net income	11	1	21	6
Tax on unrealized (loss) gain on derivatives arising during the period	0	(6)	0	36
Tax on reclassification adjustments for gain on derivatives included in net income	$ 0	$ 53	$ 0	$ 2