This element represents that the frequency of the amortization.

No definition available.

Name:	becn_AmortizationFrequency
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Period Type:	duration

- Definition

Debt outstanding.

+ References

No definition available.

+ Details

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- Definition

Line of Credit Facility, Additional Borrowing Capacity

+ References

No definition available.

+ Details

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- Definition

Description of the interest rate for the amounts borrowed under the credit facility, including the terms and the method for determining the interest rate.

+ References

No definition available.

+ Details

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- Definition

This element represents that amortization of term loan during the period

+ References

No definition available.

+ Details

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Period Type:	duration

- Definition

Represents the percentage of unused commitment fees on revolving credit facilities.

+ References

No definition available.

+ Details

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

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Period Type:	duration

- Definition

Identification of the lender and information about a contractual promise to repay a short-term or long-term obligation, which includes borrowings under lines of credit, notes payable, commercial paper, bonds payable, debentures, and other contractual obligations for payment. This may include rationale for entering into the arrangement, significant terms of the arrangement, which may include amount, repayment terms, priority, collateral required, debt covenants, borrowing capacity, call features, participation rights, conversion provisions, sinking-fund requirements, voting rights, basis for conversion if convertible and remarketing provisions. The description may be provided for individual debt instruments, rational groupings of debt instruments, or by debt in total.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
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-Paragraph 1
-Subparagraph (SX 210.5-02.22)
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Balance Type:	na
Period Type:	duration

- Definition

The average effective interest rate during the reporting period.

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-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ References

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Maximum contractual interest rate for funds borrowed, under the debt agreement.

+ References

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Minimum contractual interest rate for funds borrowed, under the debt agreement.

+ References

+ Details

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ References

+ Details

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Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

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

- Definition

Amount of debt issuance costs (for example, but not limited to, legal, accounting, broker, and regulatory fees).

+ References

No definition available.

+ Details

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

- Definition

Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 19, 20, 22
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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The fee, expressed as a percentage of the line of credit facility, for the line of credit facility regardless of whether the facility has been used.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Description of the interest rate for the amounts borrowed under the credit facility, including the terms and the method for determining the interest rate (for example, fixed or variable, LIBOR plus a percentage, increasing rate, timing of interest rate resets, remarketing provisions).

+ References

+ Details

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

- Definition

The effective interest rate during the reporting period.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

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

- Definition

The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Carrying value as of the balance sheet date of Notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer), excluding current portion. Senior note holders are paid off in full before any payments are made to junior note holders.

+ References

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

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=becn_RoofingSupplyGroupMember
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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_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
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Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=becn_TermLoanMember
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Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_LondonInterbankOfferedRateLIBORMember
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Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=becn_ConsolidatedTotalLeverageRatioMember
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- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_StandbyLettersOfCreditMember
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Balance Type:
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Name:	us-gaap_CreditFacilityAxis=becn_CanadianRevolvingCreditFacilityMember
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Balance Type:
Period Type:

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Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=becn_BaseRatesMember
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Name:	us-gaap_LongtermDebtTypeAxis=becn_LiborRateMember
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Period Type:

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Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_SeniorNotesMember
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Financing Arrangements (Additional Information) (Details) $ in Thousands, CAD in Millions	1 Months Ended	3 Months Ended		12 Months Ended
	Oct. 31, 2015 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Dec. 31, 2015 CAD	Oct. 31, 2015 CAD	Sep. 30, 2015 CAD	Sep. 30, 2012 USD ($)	Apr. 05, 2012 USD ($)	Apr. 05, 2012 CAD
Long-term Line of Credit	$ 700,000									$ 550,000
Line of Credit Facility, Interest Rate Description					higher of the Prime Rate, or the Federal Funds Rate plus 0.50%, plus a margin above that rate.
Line Of Credit Facility Rate Descriptions				higher of the Canadian Prime Rate, or the annual rate of interest equal to the sum of the CDOR rate plus 1.00%, plus a margin above that rate
Percentage Of Amortization Of Term Loan				5.00%
Line Of Credit Facility Additional Borrowing Capacity									$ 200,000
Line of Credit Facility, Interest Rate During Period				2.00%
Line of credit facility, unused fees				0.45%
Amortization Frequency				quarterly
Senior Notes Payable, Net Of Current Portion				$ 170,200	$ 183,131
Debt Issuance Cost		$ 30,000	$ 2,000	4,000
Letter of Credit [Member]
Long-term Line of Credit										20,000
Roofing Supply Group [Member]
Debt Issuance Cost		31,200
Revolving Credit Facility [Member]
Long-term Line of Credit	$ 670,000	336,000					CAD 30.0			325,000
Debt instrument, amount outstanding		$ 7,200				CAD 10.0
Line of Credit Facility, Interest Rate at Period End	2.13%						2.13%
Debt Instrument, Maturity Date	Oct. 01, 2020
Debt Instrument, Interest Rate During Period		3.20%
Percentage Of Unused Commitment Fees		0.25%				0.25%
Line of Credit Facility, Commitment Fee Percentage		10.00%
Line of Credit Facility, Maximum Borrowing Capacity		$ 60,000
Revolving Credit Facility [Member] \| Letter of Credit [Member]
Long-term Line of Credit		10,500
Revolving Credit Facility [Member] \| Subsequent Event [Member]
Long-term Line of Credit	$ 700,000
Line of Credit Facility, Maximum Borrowing Capacity	700,000
Term Loan [Member]
Long-term Line of Credit	$ 1,100	$ 437,300		$ 185,600						225,000
Line of Credit Facility, Interest Rate at Period End				4.25%	2.15%			4.25%
Debt Instrument, Maturity Date	Oct. 01, 2022
Debt Instrument, Interest Rate During Period		4.00%
Term Loan [Member] \| London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument, Interest Rate During Period		1.00%
Consolidated Total Leverage Ratio [Member]
Line of Credit Facility, Interest Rate During Period				1.00%
Standby Letters of Credit [Member]
Long-term Line of Credit				$ 4,900
Canadian Revolving Credit facility [Member]
Long-term Line of Credit				$ 11,200				CAD 15.0
Term Loan B Facility [Member]
Long-term Line of Credit		$ 450,000
Debt Instrument, Term		7 years
Base Rates [Member] \| Term Loan [Member]
Debt Instrument, Interest Rate During Period		3.00%
Libor Rate [Member]
Line of Credit Facility, Interest Rate Description				Additionally, for Base Rate borrowings made under the U.S. Revolver, the Company may elect an optional interest rate equal to the one (1), two (2), three (3), or six (6) month LIBOR rate, plus a margin above that rate
Senior Notes 2023 [Member] \| Subsequent Event [Member]
Long-term Line of Credit	$ 300,000
Line of Credit Facility, Interest Rate at Period End	6.375%						6.375%
Term Loan B [Member]
Long-term Line of Credit		$ 450,000
Debt Instrument, Term		7 years
Term Loan B [Member] \| Subsequent Event [Member]
Long-term Line of Credit	$ 450,000
Line of Credit Facility, Maximum Borrowing Capacity	$ 450,000
Senior Notes [Member]
Long-term Line of Credit		$ 700,000
Line of Credit Facility, Interest Rate at Period End		6.38%	0.00%	0.00%		6.38%		0.00%
Senior Notes Payable, Net Of Current Portion		$ 300,000
Debt Instrument, Term		8 years
Debt Instrument, Maturity Date		Oct. 01, 2023
Debt Instrument, Interest Rate During Period		6.38%
Debt Instrument, Description		semi-annually
Debt Instrument, Interest Rate, Stated Percentage		6.38%				6.38%
Senior Notes [Member] \| New Senior Credit Facilities [Member]
Debt Issuance Cost		$ 2,200
Gains (Losses) on Extinguishment of Debt, Total		$ 800
Maximum [Member]
Line of Credit Facility, Interest Rate During Period				2.50%
Line of credit facility, unused fees				0.50%
Maximum [Member] \| Revolving Credit Facility [Member]
Debt Instrument, Interest Rate During Period	4.00%
Maximum [Member] \| Consolidated Total Leverage Ratio [Member]
Line of Credit Facility, Interest Rate During Period				1.50%
Minimum [Member]
Line of Credit Facility, Interest Rate During Period				1.50%
Line of credit facility, unused fees				0.35%
Minimum [Member] \| Revolving Credit Facility [Member]
Debt Instrument, Interest Rate During Period	1.92%
Minimum [Member] \| Term Loan [Member]
Line of Credit Facility, Interest Rate at Period End					2.33%
Minimum [Member] \| Consolidated Total Leverage Ratio [Member]
Line of Credit Facility, Interest Rate During Period				0.50%
Equipment Financing Facility [Member]
Debt instrument, amount outstanding				$ 25,500
Debt instrument, fixed interest rate minimum				2.33%
Debt instrument, fixed interest rate maximum				4.49%
U.S. Senior Secured Credit Facility [Member] \| Maximum [Member] \| Base Rates [Member]
Senior notes payable to commercial lenders, interest rate margin				3.70%
U.S. Senior Secured Credit Facility [Member] \| Minimum [Member] \| Base Rates [Member]
Senior notes payable to commercial lenders, interest rate margin				1.00%
Canadian Senior Secured Credit Facility [Member] \| Maximum [Member]
Senior notes payable to commercial lenders, interest rate margin				4.25%
Canadian Senior Secured Credit Facility [Member] \| Minimum [Member]
Senior notes payable to commercial lenders, interest rate margin				1.00%
Wells Fargo Bank National Association [Member]
Long-term Line of Credit										$ 11,200	CAD 15.0