Number Of Branches Acquired

No definition available.

Name:	becn_NumberOfBranchesAcquired
Namespace Prefix:	becn_
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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 805
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479907/805-20-50-5

+ Details

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

- Definition

Amount of intangible assets, excluding goodwill, acquired at the acquisition date.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 805
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479907/805-20-50-1

+ Details

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

- Definition

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 852
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 10
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481372/852-10-55-10

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 24
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482548/350-20-55-24

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(15))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482598/350-20-45-1

Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482573/350-20-50-1

Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (h)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482573/350-20-50-1

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(10)(1))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479853/942-210-S99-1

+ Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

Acquisitions - Finite-Lived and Indefinite-Lived Intangible Assets Acquired as Part of Business Combination (Details) $ in Millions	Sep. 30, 2023 USD ($)	Sep. 05, 2023 USD ($) branch	Aug. 01, 2023 USD ($) branch	Jul. 11, 2023 USD ($) branch	Jun. 12, 2023 USD ($) branch	Mar. 31, 2023 USD ($) branch	Jan. 04, 2023 USD ($) branch	Dec. 31, 2022 USD ($)	Dec. 30, 2022 USD ($) branch	Nov. 01, 2022 USD ($) branch	Sep. 30, 2022 USD ($)	Jun. 01, 2022 USD ($) branch	Apr. 29, 2022 USD ($) branch	Jan. 01, 2022 USD ($) branch
Business Acquisition [Line Items]
Goodwill Recognized	$ 1,933.6							$ 1,916.3			$ 1,782.7
S&H Building Material Corporation
Business Acquisition [Line Items]
Branches \| branch		1
Goodwill Recognized		$ 5.7
Intangible Assets Acquired		$ 4.1
All American Vinyl Siding Supply, LLC
Business Acquisition [Line Items]
Branches \| branch			1
Goodwill Recognized			$ 0.7
Intangible Assets Acquired			$ 0.8
Crossroads Roofing Supply, Inc.
Business Acquisition [Line Items]
Branches \| branch				5
Goodwill Recognized				$ 2.5
Intangible Assets Acquired				$ 11.1
Silver State Building Materials, Inc.
Business Acquisition [Line Items]
Branches \| branch					1
Goodwill Recognized					$ 0.5
Intangible Assets Acquired					$ 0.9
Al's Roofing Supply, Inc.
Business Acquisition [Line Items]
Branches \| branch						4
Goodwill Recognized						$ 3.6
Intangible Assets Acquired						$ 7.1
Prince Building Systems, LLC
Business Acquisition [Line Items]
Branches \| branch						1
Goodwill Recognized						$ 0.6
Intangible Assets Acquired						$ 2.0
First Coastal Exteriors, LLC
Business Acquisition [Line Items]
Branches \| branch							2
Goodwill Recognized							$ 0.8
Intangible Assets Acquired							$ 1.9
Whitney Building Products
Business Acquisition [Line Items]
Branches \| branch									1
Goodwill Recognized									$ 2.7
Intangible Assets Acquired									$ 2.8
Coastal Construction Products
Business Acquisition [Line Items]
Branches \| branch										18
Goodwill Recognized										$ 133.1
Intangible Assets Acquired										$ 102.7
Complete Supply, Inc.
Business Acquisition [Line Items]
Branches \| branch												1
Goodwill Recognized												$ 8.6
Intangible Assets Acquired												$ 4.6
Wichita Falls Builders Wholesale, Inc.
Business Acquisition [Line Items]
Branches \| branch													1
Goodwill Recognized													$ 0.4
Intangible Assets Acquired													$ 0.5
Crabtree Siding and Supply
Business Acquisition [Line Items]
Branches \| branch														1
Goodwill Recognized														$ 0.1
Intangible Assets Acquired														$ 0.1