Average Lease Term Period

No definition available.

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Namespace Prefix:	bj_
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Balance Type:	na
Period Type:	duration

- Definition

Commitment And Contingencies [Line Items]

+ References

No definition available.

+ Details

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Namespace Prefix:	bj_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of rent expense incurred for leased assets, including but not limited to, furniture and equipment, that is not directly or indirectly associated with the manufacture, sale or creation of a product or product line.

+ References

No definition available.

+ Details

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

- Definition

Term of lessee's operating lease renewal, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (a)(3)
-URI http://asc.fasb.org/extlink&oid=77888426&loc=SL77918673-209980

+ Details

Name:	us-gaap_LesseeOperatingLeaseRenewalTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	instant

- Definition

Term of lessee's operating lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	instant

- Details

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Namespace Prefix:
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Balance Type:
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- Details

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Namespace Prefix:
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Balance Type:
Period Type:

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Feb. 02, 2019	Feb. 03, 2018	Jan. 28, 2017
Commitment And Contingencies [Line Items]
Average lease period	21 years
Real estate leases
Commitment And Contingencies [Line Items]
Average lease period	20 years
Rental expense	$ 308.2	$ 301.9	$ 298.1
Ground leases
Commitment And Contingencies [Line Items]
Average lease period	21 years
Equipment and equipment space
Commitment And Contingencies [Line Items]
Rental expense	$ 0.8	$ 0.7	$ 0.7
Minimum
Commitment And Contingencies [Line Items]
Renewal lease term period	5 years
Minimum \| Real estate leases
Commitment And Contingencies [Line Items]
Lease term period	5 years
Minimum \| Ground leases
Commitment And Contingencies [Line Items]
Lease term period	14 years
Maximum
Commitment And Contingencies [Line Items]
Renewal lease term period	65 years
Maximum \| Real estate leases
Commitment And Contingencies [Line Items]
Lease term period	25 years
Maximum \| Ground leases
Commitment And Contingencies [Line Items]
Lease term period	44 years