Investments - Additional Information (Details)	3 Months Ended
May 05, 2018 USD ($)
Investments, Debt and Equity Securities [Abstract]
Other-than-temporary impairments associated with credit losses	$ 0

Amount of expense to write-down the amortized cost basis of loans, after acquisition, to fair value when the decline in the fair value is determined to be other than temporary (OTTI) for loans accounted for as debt securities.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 35
-Paragraph 34D
-URI http://asc.fasb.org/extlink&oid=82895926&loc=SL6284304-111560

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 30
-Section 35
-Paragraph 8
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=82894747&loc=d3e14665-111541

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