Year when the debt instrument is scheduled to be fully repaid.

No definition available.

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- Definition

Amount of fair value of long-term debt in excess of carrying amount.

+ References

No definition available.

+ Details

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Namespace Prefix:	bmch_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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- Definition

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Description of the frequency of periodic payments (monthly, quarterly, annual).

+ 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
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-URI http://asc.fasb.org/extlink&oid=75038535&loc=d3e64711-112823

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Balance Type:	na
Period Type:	duration

- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 6
-Subparagraph (a)
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-Publisher FASB
-Name Accounting Standards Codification
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-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-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:	instant

- Definition

Date the debt instrument was issued, in CCYY-MM-DD format.

+ References

+ Details

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

- 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

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

- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571

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- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Date the credit facility first became available, in CCYY-MM-DD format.

+ References

+ Details

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Data Type:	xbrli:dateItemType
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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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

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Namespace Prefix:	us-gaap_
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Debt (Narrative) (Details) - USD ($)	Sep. 15, 2016	Dec. 01, 2015	Mar. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Date entered into agreement		Dec. 01, 2015
Maximum borrowing capacity		$ 375,000,000
Outstanding borrowings			$ 350,000,000	$ 350,000,000
Net availability			317,700,000
Letters of credit outstanding			56,100,000
Senior secured notes, due 2024 [Member]
Debt Instrument [Line Items]
Debt issuance date	Sep. 15, 2016
Outstanding borrowings	$ 350,000,000		350,000,000	350,000,000
Maturity date, year	2024
Interest rate	5.50%
Interest payment dates	payable semiannually on April 1 and October 1
Estimated market value above (below) carrying amount			(6,100,000)
Revolving credit agreement [Member]
Debt Instrument [Line Items]
Outstanding borrowings			$ 0	$ 0
Guarantor Subsidiaries [Member] \| Senior secured notes, due 2024 [Member]
Debt Instrument [Line Items]
Ownership percent	100.00%
BMC East, LLC [Member] \| Senior secured notes, due 2024 [Member]
Debt Instrument [Line Items]
Ownership percent	100.00%