Mortgage Servicing Rights - Additional Information (Detail)	9 Months Ended
Sep. 30, 2013
Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items]
Percentage of sensitivity of the current fair value	10.00%

Sensitivity Analysis Of Fair Value Of Interests Continued To Be Held By Transferor Servicing Assets Or Liabilities Percent Adverse Change In Assumption High

No definition available.

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