Cash, Cash Equivalents, and Investments (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jul. 03, 2016	Jul. 05, 2015	Jul. 03, 2016	Jul. 05, 2015
Cash and Cash Equivalents [Abstract]
Gross realized gains on sale of investments	$ 141,000	$ 210,000	$ 225,000	$ 408,000
Gross realized losses on sale of investments	0	$ 18,000	97,000	$ 187,000
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, 2017
Remaining amount of commitment in limited partnership	$ 614,000		$ 614,000
Contributions made during the period			0
Distributions received during the period			$ 0