Significant Accounting Policies - Repurchase Agreements (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012
Significant Accounting Policies Repurchase Agreements [Line Items]
Repurchase Agreement Amount At Risk	$ 9.0
[MinimumMember]
Significant Accounting Policies Repurchase Agreements [Line Items]
Repurchase Advance Amount as a Percentage of Collateral	92.00%
[MaximumMember]
Significant Accounting Policies Repurchase Agreements [Line Items]
Repurchase Advance Amount as a Percentage of Collateral	95.00%

The total amount at risk with all repurchase agreement counterparties at the end of the period. The amount at risk isthe difference between the amount loaned to the Company, including interest payable, and the fair value of the collateral pledged by the Company, including accrued interest and cash posted as collateral

No definition available.

Name:	bmnm_RepurchaseAgreementAmountAtRisk
Namespace Prefix:	bmnm_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant