Document and Entity Information Document - shares	9 Months Ended
	Dec. 31, 2020	Feb. 12, 2021
Document and Entity Information [Abstract]
Entity Registrant Name	CARVER BANCORP INC
Entity Central Index Key	0001016178
Current Fiscal Year End Date	--03-31
Entity Filer Category	Non-accelerated Filer
Document Period End Date	Dec. 31, 2020
Document Fiscal Year Focus	1905
Document Fiscal Period Focus	Q3
Amendment Flag	false
Entity Common Stock, Shares Outstanding		3,062,850
Entity Shell Company	false
Entity Emerging Growth Company	false
Document Transition Report	false