Marketable Securities Auction Rate (Details) (USD $)	9 Months Ended					0 Months Ended	3 Months Ended
	Sep. 27, 2014	Sep. 28, 2013	Dec. 28, 2013	Sep. 27, 2014 Total Auction Rate Securities	Dec. 28, 2013 Total Auction Rate Securities	Jun. 19, 2014 Federally-insured or FFELP guaranteed student loan auction rate securities	Sep. 27, 2014 Federally-insured or FFELP guaranteed student loan auction rate securities	Jun. 19, 2014 Federally-insured or FFELP guaranteed student loan auction rate securities	Dec. 28, 2013 Federally-insured or FFELP guaranteed student loan auction rate securities
Schedule of Available-for-sale Securities [Line Items]
Par value				$ 0	$ 5,700,000		$ 0	$ 5,700,000	$ 5,700,000
Available-for-sale securities	134,131,000		106,746,000	0	5,241,000		0	5,200,000	5,241,000
Proceeds from sales of auction rate securities	5,488,000	0				5,500,000
Available-for-sale securities, gross realized gain							1,700,000
Realized gain on sale of auction rate securities, previously unrealized, net of tax							$ 1,100,000