Represents compound annualized risk free rate.

No definition available.

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

- Definition

Represents amount of contributions made by the Company related to the defined hourly contribution plan.

+ References

No definition available.

+ Details

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Namespace Prefix:	bxc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Represents the estimated target allocation of investments of this type to total plan assets presented on a weighted average basis.

+ References

No definition available.

+ Details

Name:	bxc_DefinedBenefitPlanEstimatedTargetPlanAssetAllocations
Namespace Prefix:	bxc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Normal allocation of investments of this type to total plan assets presented on a weighted average basis.

+ References

No definition available.

+ Details

Name:	bxc_DefinedBenefitPlanNormalAssetAllocations
Namespace Prefix:	bxc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Defined Benefit Plans, Estimated Quarterly Future Employer Contribution in Next Fiscal Year

+ References

No definition available.

+ Details

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Namespace Prefix:	bxc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Represents amount of contributions made by the Company related to the defined salaried contribution plan.

+ References

No definition available.

+ Details

Name:	bxc_DefinedBenefitSalariedContributionPlanEmployerContributions
Namespace Prefix:	bxc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Represents expected overall portfolio return, percentage.

+ References

No definition available.

+ Details

Name:	bxc_ExpectedOverallPortfolioReturnPercentage
Namespace Prefix:	bxc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents percentage of estimated expense.

+ References

No definition available.

+ Details

Name:	bxc_ExpenseEstimatePercentage
Namespace Prefix:	bxc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents net long term rate of return.

+ References

No definition available.

+ Details

Name:	bxc_NetLongTermRateOfReturn
Namespace Prefix:	bxc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents number of collective bargaining agreements up for renewal in One Year

+ References

No definition available.

+ Details

Name:	bxc_NumberOfCollectiveBargainingAgreementsUpForRenewalinOneYear
Namespace Prefix:	bxc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents number of minimum quarterly cash contributions during the fiscal year.

+ References

No definition available.

+ Details

Name:	bxc_NumberOfMinimumRequiredQuarterlyCashContributionsDuringFiscal
Namespace Prefix:	bxc_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of employees represented by various labor unions.

+ References

No definition available.

+ Details

Name:	bxc_PercentageOfEmployeesRepresentedByVariousLaborUnions
Namespace Prefix:	bxc_
Data Type:	num: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_DefinedBenefitPlanDisclosureLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of employer's best estimate of contributions expected to be paid to the plan during the next fiscal year beginning after the date of the latest statement of financial position.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920

+ Details

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

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_EquitySecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=bxc_DomesticEquitySecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=bxc_InternationalEquitySecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_FixedIncomeFundsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=bxc_OtherInvestmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Employee Benefits - Expected Rate of Return, Investment Policy, and Multiemployer Plans - Narrative (Details) $ in Millions	12 Months Ended
	Jan. 02, 2016 USD ($) payment	Jan. 03, 2015 USD ($)	Jan. 04, 2014 USD ($)
Asset allocation structure of the portfolio
Compound annualized risk free rate	3.50%
Expected overall portfolio return percentage	8.57%
Percentage of estimated expense	0.75%
Net long term rate of return	7.82%
Number of minimum quarterly cash contributions during fiscal 2016 and 2017 \| payment	4
Quarterly future employer contribution in 2016	$ 1.0
Minimum required contribution for plan year, per quarter cash contributions during fiscal - 2016	$ 4.2
Percentages of employees represented by various labour unions	36.00%
Percentage of collective bargaining agreements up for renewal in 2016	16.00%
Contributions to the hourly defined contribution plan		$ 0.1	$ 0.1
Contributions to the salaried defined contribution plan		$ 0.9	$ 1.1
Equities
Asset allocation structure of the portfolio
Asset allocation structure of the portfolio	60.00%
Equity securities — domestic
Asset allocation structure of the portfolio
Target allocations for fiscal 2016	55.00%
Equity securities — international
Asset allocation structure of the portfolio
Target allocations for fiscal 2016	10.00%
Fixed income
Asset allocation structure of the portfolio
Asset allocation structure of the portfolio	25.00%
Target allocations for fiscal 2016	30.00%
Other
Asset allocation structure of the portfolio
Asset allocation structure of the portfolio	15.00%
Target allocations for fiscal 2016	5.00%