Segments - Narrative (Details)	9 Months Ended
Oct. 31, 2020 USD ($) state store segment province distribution_center
Segment Reporting Information [Line Items]
Number of retail discount stores \| store	15,600
Number of states/provinces the Company operates in \| state	48
Number of reporting business segments \| segment	2
Dollar Tree
Segment Reporting Information [Line Items]
Merchandise fixed price \| $	$ 1.00
Family Dollar
Segment Reporting Information [Line Items]
Number of distribution centers	11
Canada
Segment Reporting Information [Line Items]
Number of states/provinces the Company operates in \| province	5
Canada \| Dollar Tree
Segment Reporting Information [Line Items]
Number of distribution centers	2
United States \| Dollar Tree
Segment Reporting Information [Line Items]
Number of distribution centers	15

Fixed price for offering merchandise in discount variety stores

No definition available.

Name:	dltr_MerchandiseFixedPrice
Namespace Prefix:	dltr_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Number Of Distribution Centers

+ References

No definition available.

+ Details

Name:	dltr_NumberOfDistributionCenters
Namespace Prefix:	dltr_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 18
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8672-108599

+ Details

Name:	us-gaap_NumberOfReportableSegments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of states the entity operates in as of the balance sheet date.

+ References

No definition available.

+ Details

Name:	us-gaap_NumberOfStatesInWhichEntityOperates
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the number of stores.

+ References

No definition available.

+ Details

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

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

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Namespace Prefix:
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Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=dltr_FamilyDollarMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementGeographicalAxis=country_CA
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementGeographicalAxis=country_US
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: