Cash, Cash Equivalents, and Investments (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Oct. 04, 2015	Sep. 28, 2014	Oct. 04, 2015	Sep. 28, 2014
Cash and Cash Equivalents [Abstract]
Gross realized gains on sale of investments	$ 26,000	$ 66,000	$ 434,000	$ 695,000
Gross realized losses on sale of investments	7,000	$ 21,000	194,000	$ 44,000
Maximum amount committed to invest in limited partnership			20,500,000
Contribution to limited partnership	19,886,000		$ 19,886,000
Investment expiration date			Dec. 31, 2015
Remaining amount of commitment in limited partnership	614,000		$ 614,000
Number of contributions made during the period			$ 0
Distributions from Partnership during period	$ 1,014,000