Debt instrument maturity year.

No definition available.

Name:	becn_DebtInstrumentMaturityYear
Namespace Prefix:	becn_
Data Type:	xbrli:gYearItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of fixed interest rate of equipment financing facilities.

+ References

No definition available.

+ Details

Name:	becn_PercentageOfFixedInterestRateOfEquipmentFinancingFacilities
Namespace Prefix:	becn_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1B
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495323-112611

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
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

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

- Definition

Date when the debt instrument is scheduled to be fully repaid, in YYYY-MM-DD format.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(2))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1B
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495323-112611

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-URI http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258

+ Details

Name:	us-gaap_DebtInstrumentMaturityDate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Date the credit facility terminates, in YYYY-MM-DD format.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_LineOfCreditFacilityExpirationDate1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

The effective interest rate at the end of the reporting period.

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityInterestRateAtPeriodEnd
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	us-gaap_LongtermDebtTypeAxis=becn_EquipmentFinancialFacilitiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=becn_SeniorNotesDueTwoThousandTwentyFiveMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=becn_SeniorNotesDueInNovemberTwoThousandTwentySixMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=becn_SeniorNotesDueInMayFifteenTwoThousandTwentyNineMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_RevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=becn_TwoThousandAndTwentySixAssetBasedRevolvingLineOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_CreditFacilityAxis=becn_TermLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=becn_TermLoanDueInJanuaryTwoTwoThousandAndTwentyFiveMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=becn_TermLoanDueMayNineteenTwoThousandAndTwentyEightMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Financing Arrangements - Long-term Debt Instruments (Parenthetical) (Detail)				3 Months Ended
	May 19, 2021	May 10, 2021	Jan. 02, 2018	Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021	Oct. 25, 2017
Equipment Financing Facilities [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Equipment financing facilities, fixed interest rate percentage						2.33%
Equipment Financing Facilities [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Equipment financing facilities, fixed interest rate percentage						2.89%
2025 Senior Notes [Member]
Debt Instrument [Line Items]
Debt interest rate at period end						4.875%	4.875%
Debt instrument maturity year						2025
2026 Senior Notes [Member]
Debt Instrument [Line Items]
Debt interest rate at period end				4.50%	4.50%	4.50%
Debt instrument maturity date				Nov. 15, 2026	Nov. 15, 2026	Nov. 15, 2026
2029 Senior Notes [Member]
Debt Instrument [Line Items]
Debt interest rate at period end		4.125%		4.125%	4.125%
Debt instrument maturity date		May 15, 2029		May 15, 2029	May 15, 2029
Revolving Lines of Credit [Member] \| 2026 ABL Facility [Member]
Debt Instrument [Line Items]
Debt instrument maturity date	May 19, 2026
Revolving Lines of Credit [Member] \| 2026 ABL Facility [Member] \| U.S. [Member]
Debt Instrument [Line Items]
Line of credit facility, interest rate at period end				2.51%
Line of credit facility, expiration date				May 19, 2026
Term Loan [Member] \| Term Loan, Matures January 2025 [Member]
Debt Instrument [Line Items]
Debt interest rate at period end						2.36%
Debt instrument maturity date			Jan. 02, 2025			Jan. 02, 2025
Term Loan [Member] \| 2028 Term Loan [Member]
Debt Instrument [Line Items]
Debt interest rate at period end				2.46%	2.46%
Debt instrument maturity date				May 19, 2028	May 19, 2028