PENDING ACQUISITION AND RELATED DEBT Pending Acquisition (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
Jan. 31, 2015	Jul. 27, 2014
Business Acquisition [Line Items]
Business Combination, Estimated Acquisition Related Costs	$ 210.0
Business Combination, Acquisition Related Costs	75.2
Business Combination, Acquisition Related Costs Paid	33.5
Business Combination Acquisition Related Costs, recorded in Selling, General & Administrative Expense	28.5
Business Combination, Acquisition Related Interest Expense Costs	46.7
Business Combination, Estimated Acquisition Related Commitment Fees	22.6
Business Combination, Estimated Acquisition Capitalizable Debt Issuance Costs	174.0
Business Combination, Contingent Consideration, Asset	70.2
Business Combination, Contingent Consideration, Liability	$ 112.0
Family Dollar [Member]
Business Acquisition [Line Items]
Business Acquisition, Share Price		$ 59.60
Maximum [Member] \| Family Dollar [Member] \| Common Stock [Member]
Business Acquisition [Line Items]
Conversion of Stock, Shares Converted	0.3036
Minimum [Member] \| Family Dollar [Member] \| Common Stock [Member]
Business Acquisition [Line Items]
Conversion of Stock, Shares Converted	0.2484

Business Combination, Acquisition Related Costs Paid

No definition available.

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

- Definition

Business Combination Acquisition Related Costs, recorded in Selling, General & Administrative Expense

+ References

No definition available.

+ Details

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

- Definition

Business Combination, Acquisition Related Interest Expense Costs

+ References

No definition available.

+ Details

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

- Definition

Business Combination, Estimated Acquisition Capitalizable Debt Issuance Costs

+ References

No definition available.

+ Details

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

- Definition

Business Combination, Estimated Acquisition Related Commitment Fees

+ References

No definition available.

+ Details

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

- Definition

Merger related costs expected to incur on or before closing of proposed acquisition.

+ References

No definition available.

+ Details

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

- Details

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

- Definition

Price of a single share of a number of saleable stocks paid or offered to be paid in a business combination.

+ References

No definition available.

+ Details

Name:	us-gaap_BusinessAcquisitionSharePrice
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 10

-Section 25

-Paragraph 23

-URI http://asc.fasb.org/extlink&oid=34752592&loc=d3e1043-128460

+ Details

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

- Definition

Amount of asset recognized arising from contingent consideration in a business combination.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 30

-Section 35

-Paragraph 1

-Subparagraph b

-URI http://asc.fasb.org/extlink&oid=6911338&loc=d3e6819-128478

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 30

-Section 25

-Paragraph 7

-URI http://asc.fasb.org/extlink&oid=6911189&loc=d3e6411-128476

+ Details

Name:	us-gaap_BusinessCombinationContingentConsiderationAsset
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of liability recognized arising from contingent consideration in a business combination.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 30

-Section 25

-Paragraph 6

-URI http://asc.fasb.org/extlink&oid=6911189&loc=d3e6408-128476

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 30

-Section 35

-Paragraph 1

-Subparagraph b

-URI http://asc.fasb.org/extlink&oid=6911338&loc=d3e6819-128478

+ Details

Name:	us-gaap_BusinessCombinationContingentConsiderationLiability
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The number of shares converted in a noncash (or part noncash) transaction. Noncash is defined as transactions during a period that do not result in cash receipts or cash payments in the period. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 50

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4332-108586

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 50

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4313-108586

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 50

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4304-108586

+ Details

Name:	us-gaap_ConversionOfStockSharesConverted1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Details

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

- Details

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: