Employee Stock Ownership Plan - Employee Stock Ownership Plan (ESOP) Disclosures (Parenthetical) (Detail)	12 Months Ended
Dec. 31, 2019 $ / shares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Fair Value of Unallocated Shares Of ESOP Share Price	$ 10.78

Represents Fair Value of Unallocated Shares Of ESOP Share Price.

No definition available.

Name:	bcow_FairValueOfUnallocatedSharesOfEsopSharePrice
Namespace Prefix:	bcow_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration