Basis of Presentation and Summary of Significant Accounting Policies (Policies)	9 Months Ended
Oct. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Fiscal Period, Policy [Policy Text Block]	Fiscal Periods Our fiscal year ends on the Saturday nearest to January 31, which results in fiscal years consisting of 52 or 53 weeks. Unless otherwise stated, references to years in this report relate to fiscal years rather than calendar years. Fiscal year 2020 (“2020”) is comprised of the 52 weeks that began on February 2, 2020 and will end on January 30, 2021. Fiscal year 2019 (“2019”) was comprised of the 52 weeks that began on February 3, 2019 and ended on February 1, 2020. The fiscal quarters ended October 31, 2020 (“third quarter of 2020”) and November 2, 2019 (“third quarter of 2019”) were both comprised of 13 weeks. The year-to-date periods ended October 31, 2020 (“year-to-date 2020") and November 2, 2019 (“year-to-date 2019”) were both comprised of 39 weeks.
Cash and Cash Equivalents, Policy	Cash and Cash Equivalents Cash and cash equivalents primarily consist of amounts on deposit with financial institutions, outstanding checks, credit and debit card receivables, and highly liquid investments, including money market funds, treasury bills and commercial paper, which are unrestricted to withdrawal or use and which have an original maturity of three months or less. We review cash and cash equivalent balances on a bank by bank basis in order to identify book overdrafts. Book overdrafts occur when the aggregate amount of outstanding checks and electronic fund transfers exceed the cash deposited at a given bank. We reclassify book overdrafts, if any, to accounts payable on our consolidated balance sheets.
Selling, General and Administrative Expenses, Policy [Policy Text Block]	Selling and Administrative Expenses Selling and administrative expenses include store expenses (such as payroll and occupancy costs) and costs related to warehousing, distribution, outbound transportation to our stores, advertising, purchasing, insurance, non-income taxes, accepting credit/debit cards, and overhead. Our selling and administrative expense rates may not be comparable to those of other retailers that include warehousing, distribution, and outbound transportation costs in cost of sales. Warehousing, distribution, and outbound transportation costs included in selling and administrative expenses were $66.3 million and $48.8 million for the third quarter of 2020 and the third quarter of 2019, respectively, and $178.3 million and $137.1 million for the year-to-date 2020 and the year-to-date 2019, respectively.
Advertising Cost [Policy Text Block]	Advertising Expense Advertising costs, which are expensed as incurred, consist primarily of television and print advertising, digital, social media, internet and e-mail marketing and advertising, and in-store point-of-purchase signage and presentations. Advertising expenses are included in selling and administrative expenses. Advertising expenses were $24.4 million and $18.2 million for the third quarter of 2020 and the third quarter of 2019, respectively, and $69.2 million and $57.9 million for the year-to-date 2020 and the year-to-date 2019, respectively.
Derivatives, Policy [Policy Text Block]	Derivative Instruments We use derivative instruments to mitigate the risk of market fluctuations in the price of diesel fuel that we expect to consume to support our outbound transportation of inventory to our stores. We do not enter into derivative instruments for speculative purposes. Our derivative instruments may consist of collar or swap contracts. Our current derivative instruments do not meet the requirements for cash flow hedge accounting. Instead, our derivative instruments are marked-to-market to determine their fair value and any gains or losses are recognized currently in other income (expense) on our consolidated statements of operations and comprehensive income.
Comparability of Prior Year Financial Data, Policy [Policy Text Block]	Reclassification of Merchandise CategoriesWe periodically assess, and make minor adjustments to, our product hierarchy, which can impact the roll-up of our merchandise categories. Our financial reporting process utilizes the most current product hierarchy in reporting net sales by merchandise category for all periods presented. Therefore, there may be minor reclassifications of net sales by merchandise category compared to previously reported amounts.
New Accounting Pronouncements, Policy [Policy Text Block]	Recently Adopted Accounting StandardsIn August 2018, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2018-15 Intangibles - Goodwill and Other - Internal-Use Software. This update evaluates the accounting for costs paid by a customer to implement a cloud computing arrangement. The new guidance aligns cloud computing arrangement implementation cost accounting with the capitalization requirements for internal-use software development, while leaving the accounting for service elements unchanged. On February 2, 2020, we adopted ASU 2018-15 on a prospective basis. The impact of the adoption was immaterial to the consolidated financial statements.

Basis of Presentation and Summary of Significant Accounting Policies (Policies)

9 Months Ended

Oct. 31, 2020

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Fiscal Period, Policy [Policy Text Block]

Fiscal Periods

Our fiscal year ends on the Saturday nearest to January 31, which results in fiscal years consisting of 52 or 53 weeks. Unless otherwise stated, references to years in this report relate to fiscal years rather than calendar years. Fiscal year 2020 (“2020”) is comprised of the 52 weeks that began on February 2, 2020 and will end on January 30, 2021. Fiscal year 2019 (“2019”) was comprised of the 52 weeks that began on February 3, 2019 and ended on February 1, 2020. The fiscal quarters ended October 31, 2020 (“third quarter of 2020”) and November 2, 2019 (“third quarter of 2019”) were both comprised of 13 weeks. The year-to-date periods ended October 31, 2020 (“year-to-date 2020") and November 2, 2019 (“year-to-date 2019”) were both comprised of 39 weeks.

Cash and Cash Equivalents, Policy

Cash and Cash Equivalents

Cash and cash equivalents primarily consist of amounts on deposit with financial institutions, outstanding checks, credit and debit card receivables, and highly liquid investments, including money market funds, treasury bills and commercial paper, which are unrestricted to withdrawal or use and which have an original maturity of three months or less. We review cash and cash equivalent balances on a bank by bank basis in order to identify book overdrafts. Book overdrafts occur when the aggregate amount of outstanding checks and electronic fund transfers exceed the cash deposited at a given bank. We reclassify book overdrafts, if any, to accounts payable on our consolidated balance sheets.

Selling, General and Administrative Expenses, Policy [Policy Text Block]

Selling and Administrative Expenses

Selling and administrative expenses include store expenses (such as payroll and occupancy costs) and costs related to warehousing, distribution, outbound transportation to our stores, advertising, purchasing, insurance, non-income taxes, accepting credit/debit cards, and overhead. Our selling and administrative expense rates may not be comparable to those of other retailers that include warehousing, distribution, and outbound transportation costs in cost of sales. Warehousing, distribution, and outbound transportation costs included in selling and administrative expenses were $66.3 million and $48.8 million for the third quarter of 2020 and the third quarter of 2019, respectively, and $178.3 million and $137.1 million for the year-to-date 2020 and the year-to-date 2019, respectively.

Advertising Cost [Policy Text Block]

Advertising Expense

Advertising costs, which are expensed as incurred, consist primarily of television and print advertising, digital, social media, internet and e-mail marketing and advertising, and in-store point-of-purchase signage and presentations. Advertising expenses are included in selling and administrative expenses. Advertising expenses were $24.4 million and $18.2 million for the third quarter of 2020 and the third quarter of 2019, respectively, and $69.2 million and $57.9 million for the year-to-date 2020 and the year-to-date 2019, respectively.

Derivatives, Policy [Policy Text Block]

Derivative Instruments

We use derivative instruments to mitigate the risk of market fluctuations in the price of diesel fuel that we expect to consume to support our outbound transportation of inventory to our stores. We do not enter into derivative instruments for speculative purposes. Our derivative instruments may consist of collar or swap contracts. Our current derivative instruments do not meet the requirements for cash flow hedge accounting. Instead, our derivative instruments are marked-to-market to determine their fair value and any gains or losses are recognized currently in other income (expense) on our consolidated statements of operations and comprehensive income.

Comparability of Prior Year Financial Data, Policy [Policy Text Block]

Reclassification of Merchandise CategoriesWe periodically assess, and make minor adjustments to, our product hierarchy, which can impact the roll-up of our merchandise categories. Our financial reporting process utilizes the most current product hierarchy in reporting net sales by merchandise category for all periods presented. Therefore, there may be minor reclassifications of net sales by merchandise category compared to previously reported amounts.

New Accounting Pronouncements, Policy [Policy Text Block]

Recently Adopted Accounting StandardsIn August 2018, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2018-15 Intangibles - Goodwill and Other - Internal-Use Software. This update evaluates the accounting for costs paid by a customer to implement a cloud computing arrangement. The new guidance aligns cloud computing arrangement implementation cost accounting with the capitalization requirements for internal-use software development, while leaving the accounting for service elements unchanged. On February 2, 2020, we adopted ASU 2018-15 on a prospective basis. The impact of the adoption was immaterial to the consolidated financial statements.