Investments - Summary Of Unrealized Gains (Losses) On Investments (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jul. 26, 2015	Jul. 27, 2014	Jul. 26, 2015	Jul. 27, 2014
Investments [Abstract]
Unrealized gain (loss), net of tax	$ 84	$ (1)	$ 138	$ 0
Increase to deferred tax liability	$ 56	$ (1)	$ 98	$ 0

The change in unrealized holding gain (loss), net of tax, on available-for-sale securities included in a separate component of shareholders' equity during the period.

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=27724398&loc=d3e27357-111563

Name:	us-gaap_AvailableForSaleSecuritiesChangeInNetUnrealizedHoldingGainLossNetOfTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration