Leases - Schedule of Right-of-Use Assets and the Corresponding Lease Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Right-of-use assets	$ 6,865	$ 8,411
Lease liabilities	$ 7,218	$ 8,792
Operating Lease, Liability, Statement of Financial Position [Extensible List]	bmi:OtherGeographicalAreasMember	bmi:OtherGeographicalAreasMember