Investments - Additional Information (Detail) (USD $)	3 Months Ended
Mar. 30, 2013 Y	Dec. 29, 2012 Y
Schedule of Available-for-sale Securities [Line Items]
Investments, maximum maturity period, years	5	5
Unrealized gains, net of unrealized losses, on the investments in the bond portfolio	$ 1,318,000	$ 1,407,000

The net amount of gross unrealized gains (losses) for securities, at a point in time, which are categorized neither as held-to-maturity nor trading securities.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 9

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=6872113&loc=d3e27357-111563

Name:	us-gaap_AvailableForSaleSecuritiesGrossUnrealizedGainLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant