Summary of Significant Accounting Policies (Details)	9 Months Ended
Sep. 30, 2012
Summary of Significant Accounting Policies [Abstract]
Percentage of original or adjusted cost exceeding unrealized loss (in hundredths)	20.00%

This line item represents percentage of original or adjusted cost exceeding unrealized loss for any equity security during the reporting period.

No definition available.

Name:	bwinb_PercentageOfAdjustedCostExceedingUnrealizedLoss
Namespace Prefix:	bwinb_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration