Description of the Business and Summary of Significant Accounting Policies (Details)	Mar. 31, 2020
Description of the Business and Summary of Significant Accounting Policies
Loans with LIBOR index rate (as a percent)	10.70%

Percentage of loans with variable or adjustable rate of interest.

No definition available.

Name:	bwb_LoansReceivableWithVariableRatesOfInterestPercent
Namespace Prefix:	bwb_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant