Cover Page - shares	9 Months Ended
	Sep. 30, 2020	Nov. 12, 2020
Cover [Abstract]
Document Type	10-Q
Document Period End Date	Sep. 30, 2020
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q3
Trading Symbol	BCOW
Entity Registrant Name	1895 Bancorp of Wisconsin, Inc.
Entity Central Index Key	0001751692
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Shell Company	false
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Address, State or Province	WI
Entity Interactive Data Current	Yes
Title of 12(b) Security	Common Stock
Security Exchange Name	NASDAQ
Entity Common Stock, Shares Outstanding		4,769,952
Entity File Number	001-38778
Entity Tax Identification Number	83-3178316
Entity Address, Address Line One	7001 West Edgerton Avenue
Entity Address, City or Town	Greenfield
Entity Address, Postal Zip Code	53220
City Area Code	414
Local Phone Number	421-8200
Entity Incorporation, State or Country Code	X1
Document Quarterly Report	true
Document Transition Report	false