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

The carrying amount of the liability as of the balance sheet date to an individual under a deferred compensation arrangement. This amount may be the result of periodic accruals made over the period of active employment, or reflect termination benefits resulting contractual terms or a death benefit.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 710
-SubTopic 10
-Section 30
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6409875&loc=d3e20015-108363

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

Weighted average rate for present value of future retirement benefits cash flows, used to determine net periodic benefit cost of defined benefit plan.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (k)(1)
-URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920

Name:	us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostDiscountRate
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan.

No definition available.

Name:	us-gaap_DefinedContributionPlanEmployerMatchingContributionPercent
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

Percentage employer matches of the employee's percentage contribution matched.

No definition available.

Name:	us-gaap_DefinedContributionPlanEmployerMatchingContributionPercentOfMatch
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

Maximum percentage of employee gross pay the employee may contribute to a defined contribution plan.

No definition available.

Name:	us-gaap_DefinedContributionPlanMaximumAnnualContributionsPerEmployeePercent
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

The amount of plan compensation cost recognized during the period.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 40
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=109244661&loc=d3e17540-113929

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

Name:	us-gaap_EmployeeStockOwnershipPlanESOPDisclosuresByPlanAxis=bmi_DefinedContributionFeatureMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_RetirementPlanTypeAxis=us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_RetirementPlanTaxStatusAxis=us-gaap_QualifiedPlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_TitleOfIndividualAxis=bmi_OfficersAndKeyEmployeesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: