Income Taxes - REIT Activities (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2012
Real Estate Investment Trust Activities [Abstract]
REIT Tax Net Operating Loss Carryforward	$ 13.8
REIT Net Operating Loss Carryover Expiration	2028 through 2032

The expiration date of each operating loss carryforward included in total operating loss carryforwards, or the applicable range of such expiration dates.

No definition available.

Name:	bmnm_ReitOperatingLossCarryoverExpiration
Namespace Prefix:	bmnm_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration