Earnings Per Share - Earnings Per Common Share (Parenthetical) (Detail)	Dec. 31, 2021	Jul. 14, 2021
Common stock shares conversion ratio as part of offering pursuant to share based scheme	1.3163	1.3163

Common stock shares conversion ratio as part of offering pursuant to share based scheme.

No definition available.

Name:	bcow_CommonStockSharesConversionRatioAsPartOfOfferingPursuantToShareBasedScheme
Namespace Prefix:	bcow_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant