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Document and Entity Information Document - shares
 6 Months Ended
Sep. 30, 2018
Nov. 12, 2018
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 Type 10-Q  
Document Period End Date Sep. 30, 2018  
Document Fiscal Year Focus 2019  
Document Fiscal Period Focus Q2  
Amendment Flag false  
Entity Common Stock, Shares Outstanding   3,698,664
Entity Smaller Reporting Company true  
Entity Emerging Growth Company false  
Entity Current Reporting Status Yes