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v3.20.2

Note 16 - Subsequent Events (Details Textual) | 1 Months Ended
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Aug. 06, 2020 USD ($)
Non-voting Preferred Units of DFH LLC [Member] | Subsequent Event [Member] |
Redemption of Preferred Units | $ 6,000,000

X
- Definition The value of preferred units redeemed. + References No definition available. + Details
Name: | bomn_RedemptionOfPreferredUnits
Namespace Prefix: | bomn_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | us-gaap_InvestmentTypeAxis=bomn_NonvotingPreferredUnitsOfDFHLLCMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |