Investments - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Oct. 28, 2018	Oct. 29, 2017	Jan. 27, 2019	Jan. 28, 2018	Jan. 29, 2017
Investments [Abstract]
Impairment of investments	$ 30,000	$ 4,300	$ 30,000	$ 4,250	$ 0

Amount of impairment loss on investment in equity security without readily determinable fair value.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 321
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84241550&loc=SL75117539-209714

Name:	us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueImpairmentLossAnnualAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration