Carver Bancorp Inc.-Parent Company Only-Condensed Statements of Financial Condition (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2019
Condensed Balance Sheet Statements, Captions [Line Items]
Other assets	$ 5,287	$ 5,853
Total assets	676,748	578,770
Other liabilities	14,663	9,335
Total liabilities	624,447	529,876
Stockholders' Equity Attributable to Parent	52,301	48,894	$ 47,136
Total liabilities and equity	676,748	578,770
Parent Company
Condensed Balance Sheet Statements, Captions [Line Items]
Cash on deposit with subsidiaries	12,374	496	$ 495
Investment in subsidiaries	63,871	65,018
Other assets	363	161
Total assets	76,608	65,675
Borrowings	13,403	13,403
Accounts payable to subsidiaries	7,656	739
Other liabilities	3,248	2,639
Total liabilities	24,307	16,781
Stockholders' Equity Attributable to Parent	52,301	48,894
Total liabilities and equity	$ 76,608	$ 65,675