Accounting for Uncertainty in Income Taxes - Additional Information (Detail)	9 Months Ended
Sep. 30, 2013
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Likelihood of tax benefit realized upon ultimate settlement tax benefit sustained	50.00%

Likelihood Of Sustaining Tax Position Upon Examination

No definition available.

Name:	bmtc_LikelihoodOfSustainingTaxPositionUponExamination
Namespace Prefix:	bmtc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration