Carver Bancorp Inc.-Parent Company Only Parent Company Only-Condensed Statements of Operations (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2017	Mar. 31, 2016
Condensed Income Statements, Captions [Line Items]
Interest expense on borrowings									$ 1,257	$ 1,336	[1],[2]
Salaries and employee benefits									12,548	11,358	[1],[3]
Shareholder expense									296	337
Other									8,899	8,744	[1],[4]
Net loss	$ (2,034)	$ (893)	$ (251)	$ 325	$ (1,489)	$ 156	$ (563)	$ 129	(2,853)	(1,767)	[1],[3],[5]
Comprehensive loss									(4,486)	(1,029)	[1]
Parent Company
Condensed Income Statements, Captions [Line Items]
Equity in net loss from subsidiaries									(2,048)	(767)	[4],[6]
Other income									26	23
Total income									(2,022)	(744)	[4]
Interest expense on borrowings									568	531	[5]
Salaries and employee benefits									0	237
Shareholder expense									82	82
Other									181	173
Total expense									831	1,023	[7]
Net loss									$ (2,853)	$ (1,767)	[4],[6]

[1] (1) March 31, 2016 balances have been restated from previously reported results to correct for material and certain other errors from prior periods. Refer to Notes 1 and 19 for further detail.

[2] (a) March 31, 2016 balances have been restated from previously reported results to correct for material and certain other errors from prior periods. Refer to Notes 1 and 19 for further detail.

[3] (1) March 31, 2015 and 2016 balances have been restated from previously reported results to correct for material and certain other errors from prior periods. Refer to Notes 1 and 19 for further detail.

[4] (1) March 31, 2016 balances have been restated from previously reported results to correct for material and certain other errors from prior periods. Refer to Notes 1 and 19 for further detail.

[5] (1) March 31, 2016 balances have been restated from previously reported results to correct for material and certain other errors from prior periods. Net loss was increased by $1.6 million, equity in net loss of subsidiaries was increased by $1.5 million and increase in other liabilities was increased by $66 thousand. Refer to Notes 1 and 19 for further detail.

[6] (1) March 31, 2016 balances have been restated from previously reported results to correct for material and certain other errors from prior periods. Refer to Notes 1 and 19 for further detail.

[7] (1) March 31, 2016 balances have been restated from previously reported results to correct for material and certain other errors from prior periods. Investment in subsidiaries, total assets and total liabilities and stockholders' equity were each reduced by $2.2 million, other liabilities and total liabilities increased by $157 thousand and stockholders' equity was reduced by $2.3 million. Refer to Notes 1 and 19 for further detail.