Summary of Significant Accounting Policies - Additional Information (Detail)				3 Months Ended								12 Months Ended
	Oct. 01, 2018 USD ($) $ / shares shares	Jul. 02, 2018 USD ($) $ / shares shares	Jun. 15, 2018	Feb. 02, 2019 USD ($)	Nov. 03, 2018 USD ($)	Aug. 04, 2018 USD ($)	May 05, 2018 USD ($)	Feb. 03, 2018 USD ($)	Oct. 28, 2017 USD ($)	Jul. 29, 2017 USD ($)	Apr. 29, 2017 USD ($)	Feb. 02, 2019 USD ($) reporting_unit shares	Feb. 03, 2018 USD ($)	Jan. 28, 2017 USD ($)	Feb. 03, 2019 USD ($)	Feb. 04, 2018 USD ($)
Accounting Policies [Abstract]
Deferred revenue, remaining performance obligations				$ 13,400,000								$ 13,400,000
Significant Accounting Policies [Line Items]
Aggregate net offering proceeds												690,970,000	$ 0	$ 0
Stock issuance costs												5,081,000	0	0
Repayment of debt												975,633,000	0	0
Stock split, conversion ratio			7
Allowances for doubtful accounts				900,000				$ 1,200,000				900,000	1,200,000
Depreciation expense												140,400,000	138,000,000	149,500,000
Amortization of deferred debt issuance costs												$ 3,322,000	4,060,000	7,693,000
Number of reporting units for goodwill impairment testing | reporting_unit												1
Impairment of goodwill												$ 0	0	0
Impairment of long-lived assets												$ 4,000,000	0	0
Percentage of cash back earned												2.00%
Maximum annual cash back amount												$ 500
Cash back in form of electronic awards issued												$ 20
Cash back in form of electronic awards issued, expiration term												6 months
Other current liabilities				25,800,000				22,700,000				$ 25,800,000	22,700,000
Accumulated deficit				915,113,000				1,036,012,000				915,113,000	1,036,012,000			$ 1,042,374,000
Sales returns reserve												6,800,000	1,500,000	$ 2,000,000
Gross amount of assets recorded under capital lease and financing obligations				41,600,000				49,400,000				41,600,000	49,400,000
Accumulated depreciation for capital lease				12,600,000				12,200,000				$ 12,600,000	$ 12,200,000
Advertising expenses as a percent of net sales												0.70%	0.60%	0.50%
Cost of sales												$ 10,646,452,000	$ 10,513,492,000	$ 10,223,017,000
Net sales				3,416,882,000	$ 3,221,663,000	$ 3,307,105,000	$ 3,061,697,000	3,555,989,000	$ 3,084,245,000	$ 3,167,527,000	$ 2,946,828,000	$ 13,007,347,000	12,754,589,000	12,350,537,000
Membership
Significant Accounting Policies [Line Items]
Membership term												12 months
Deferred revenue				134,400,000				125,600,000				$ 134,400,000	125,600,000
Revenue recognized												282,893,000	258,594,000
Net sales												282,893,000	258,594,000	255,235,000
Gift Card Programs
Significant Accounting Policies [Line Items]
Deferred revenue				9,100,000								9,100,000				8,800,000
Revenue recognized												50,000,000
Product
Significant Accounting Policies [Line Items]
Net sales				3,343,814,000	$ 3,150,234,000	$ 3,236,664,000	$ 2,993,742,000	$ 3,489,973,000	$ 3,019,389,000	$ 3,103,335,000	$ 2,883,298,000	12,724,454,000	12,495,995,000	12,095,302,000
BJ’s trade name
Significant Accounting Policies [Line Items]
Impairment of indefinite-lived intangible assets												$ 0	$ 0	$ 0
Minimum | ASU 2016-02 | Scenario, Forecast
Significant Accounting Policies [Line Items]
Operating lease liabilities															$ 1,900,000,000
Minimum | My BJ's Perks Mastercard
Significant Accounting Policies [Line Items]
Percentage of cash back earned												3.00%
Minimum | Card outside of BJ's
Significant Accounting Policies [Line Items]
Percentage of cash back earned												1.00%
Maximum | ASU 2016-02 | Scenario, Forecast
Significant Accounting Policies [Line Items]
Operating lease liabilities															$ 2,100,000,000
Maximum | My BJ's Perks Mastercard
Significant Accounting Policies [Line Items]
Percentage of cash back earned												5.00%
Maximum | Card outside of BJ's
Significant Accounting Policies [Line Items]
Percentage of cash back earned												2.00%
Buildings and improvements
Significant Accounting Policies [Line Items]
Estimated useful life												33 years
Furniture, fixtures and equipment | Minimum
Significant Accounting Policies [Line Items]
Estimated useful life												3 years
Furniture, fixtures and equipment | Maximum
Significant Accounting Policies [Line Items]
Estimated useful life												10 years
Software | Minimum
Significant Accounting Policies [Line Items]
Estimated useful life												3 years
Software | Maximum
Significant Accounting Policies [Line Items]
Estimated useful life												7 years
Net sales | Geographic concentration risk | New York metropolitan area
Significant Accounting Policies [Line Items]
Concentration risk percentage												25.00%	25.00%	25.00%
Net sales | Revenue from rights concentration risk
Significant Accounting Policies [Line Items]
Concentration risk percentage												97.00%
Revenues | Revenue from rights concentration risk
Significant Accounting Policies [Line Items]
Concentration risk percentage												95.00%
Second Lien Term Loan
Significant Accounting Policies [Line Items]
Repayment of debt		$ 623,300,000
Common Stock
Significant Accounting Policies [Line Items]
Common stock issued (in shares) | shares												43,125,000
Accumulated Other Comprehensive Income
Significant Accounting Policies [Line Items]
Reclassification of stranded tax effects from Tax Cuts and Jobs Act													$ (432,000)
Accumulated Deficit
Significant Accounting Policies [Line Items]
Reclassification of stranded tax effects from Tax Cuts and Jobs Act													$ 432,000
IPO
Significant Accounting Policies [Line Items]
Reduction to additional paid-in capital for deferred offering costs		$ 47,200,000
IPO | Common Stock
Significant Accounting Policies [Line Items]
Common stock issued (in shares) | shares	32,200,000	43,125,000
Common stock, offering price (in usd per share) | $ / shares	$ 26.00	$ 17.00
Aggregate net offering proceeds		$ 685,900,000
Stock issuance costs	$ 2,400,000	$ 47,200,000
Underwriters' option | Common Stock
Significant Accounting Policies [Line Items]
Common stock issued (in shares) | shares	4,200,000	5,625,000
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-02-03
Accounting Policies [Abstract]
Deferred revenue, remaining performance obligations				$ 11,500,000								$ 11,500,000
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Deferred revenue, remaining performance obligations, period of recognition				1 year								1 year
Difference between Revenue Guidance in Effect before and after Topic 606 | ASU 2014-09
Significant Accounting Policies [Line Items]
Accumulated deficit				$ 6,974,000								$ 6,974,000				6,362,000
Cost of sales												(5,700,000)
Difference between Revenue Guidance in Effect before and after Topic 606 | Gift Card Programs | ASU 2014-09
Significant Accounting Policies [Line Items]
Accumulated deficit																$ 1,800,000
Difference between Revenue Guidance in Effect before and after Topic 606 | Product | ASU 2014-09
Significant Accounting Policies [Line Items]
Net sales												$ (6,800,000)