Equity and Regulatory Matters - Additional Information (Detail)	Jan. 01, 2019
Subsequent Event [Member]
Capital conservation buffer	2.50%

Percentage of capital conservation buffer percentage.

No definition available.

Name:	bcow_CapitalConservationBufferPercentage
Namespace Prefix:	bcow_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration