Carver Bancorp Inc.-Parent Company Only Parent Company Only-Condensed Statements of Cash Flow (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 Cash Flow Statements, Captions [Line Items]
Net loss	$ (2,034)	$ (893)	$ (251)	$ 325	$ (1,489)	$ 156	$ (563)	$ 129	$ (2,853)	$ (1,767)	[1],[2],[3]
Decrease (increase) in other assets									1,641	(972)	[1],[2]
Increase in other liabilities									(147)	1,470	[1],[2]
Net Cash Used in Operating Activities									827	420	[1],[2]
Net decrease in cash									(4,502)	12,364	[1],[2]
Parent Company
Condensed Cash Flow Statements, Captions [Line Items]
Net loss									(2,853)	(1,767)	[4],[5]
Equity in net loss from subsidiaries									(2,048)	(767)	[4],[5]
Increase in account receivable from subsidiaries									0	(1)
Decrease (increase) in other assets									54	(14)
Increase (decrease) in accounts payable to subsidiaries									176	(1,199)
Increase in other liabilities									(1,928)	530
Net Cash Used in Operating Activities									(2,503)	(1,684)
Net decrease in cash									(2,503)	(1,684)
Cash and cash equivalents - beginning				$ 2,995				$ 4,679	2,995	4,679
Cash and cash equivalents - end	$ 492				$ 2,995				$ 492	$ 2,995

[1] (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.

[2] (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.

[3] (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.

[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. Refer to Notes 1 and 19 for further detail.