Summary of Significant Accounting Policies - Profile - Narrative (Details)	12 Months Ended
Dec. 31, 2019 Product_line
Accounting Policies [Abstract]
Number of product lines	2
Percentage of products used in water and water related applications (as a percent)	90.00%

Percentage of products used in water and water related applications.

No definition available.

Name:	bmi_PercentageOfProductsUsedInWaterAndWaterRelatedApplications
Namespace Prefix:	bmi_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration