Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=118942338&loc=SL82898722-210454

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118954083&loc=d3e26610-111562

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563

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

Investments - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
Investments - Narrative (Details) - USD ($) $ in Thousands	Oct. 27, 2019	Oct. 28, 2018	Oct. 27, 2019	Oct. 28, 2018	Jan. 27, 2019
Investment [Line Items]
Debt securities available for sale	$ 7,847		$ 7,847		$ 3,105
Investment impairments	0	$ (30,000)	0	$ (30,000)
Convertible debt
Investment [Line Items]
Debt securities available for sale	$ 7,847		$ 7,847		$ 3,105
Convertible Debt
Investment [Line Items]
Interest rate	12.00%		12.00%
Privately Held Company (The Investee) \| Convertible debt
Investment [Line Items]
Debt securities available for sale	$ 3,200		$ 3,200