Name:	bmch_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoptionNotBooked
Namespace Prefix:	bmch_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Amount of increase (decrease) in right to consideration in exchange for good or service transferred to customer when right is conditioned on something other than passage of time.

No definition available.

Name:	bmch_IncreaseDecreaseInContractWithCustomerAsset
Namespace Prefix:	bmch_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Amount of increase (decrease) in obligation to transfer good or service to customer for which consideration has been received or is receivable.

No definition available.

Name:	bmch_IncreaseDecreaseInContractWithCustomerLiability
Namespace Prefix:	bmch_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Goods and service for performance obligation satisfied over time, percentage of revenue.

No definition available.

Name:	bmch_RevenuePerformanceObligationSatisfiedOverTimePercentageOfRevenue
Namespace Prefix:	bmch_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Amount of revenue recognized that was previously included in balance of obligation to transfer good or service to customer for which consideration from customer has been received or is due.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 8
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82913847&loc=SL49130549-203045

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 270
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=84173487&loc=SL51747714-108306

Name:	us-gaap_ContractWithCustomerLiabilityRevenueRecognized
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

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.

No definition available.