JUNIOR SUBORDINATED DEBENTURES - Additional Information (Details)	6 Months Ended
	Sep. 30, 2021 USD ($) item	Mar. 31, 2021 USD ($)
JUNIOR SUBORDINATED DEBENTURES
Maximum number of consecutive quarters for deferred payment of each debenture | item	20
Debentures issued to grantor trusts	$ 26,800,000	$ 26,700,000
Common securities issued by grantor trusts	$ 836,000	$ 836,000
Riverview Bancorp Statutory Trust I
JUNIOR SUBORDINATED DEBENTURES
Description of variable rate	three-month LIBOR
Interest basis spread on variable rate	1.36%
Riverview Bancorp Statutory Trust II
JUNIOR SUBORDINATED DEBENTURES
Description of variable rate	three-month LIBOR
Interest basis spread on variable rate	1.35%
Merchants Bancorp Statutory Trust I
JUNIOR SUBORDINATED DEBENTURES
Description of variable rate	three-month LIBOR
Interest basis spread on variable rate	3.10%