Note 3 - Financial Instruments Measured at Fair Value (Details Textual) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 30, 2017
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	$ 14.7	$ 13.2

This item represents the aggregate fair value of investments in debt and equity securities in an unrealized loss position which are categorized neither as held-to-maturity nor trading securities.

No definition available.

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