INVESTMENT SECURITIES - Fair value of impaired investment securities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Mar. 31, 2021
INVESTMENT SECURITIES
Less than 12 months, Estimated Fair Value	$ 176,967	$ 105,317
Less than 12 months, Unrealized Losses	(2,562)	(2,460)
12 months or longer, Estimated Fair Value	1,331	2,225
12 months or longer, Unrealized Losses	(18)	(51)
Total, Estimated Fair Value	178,298	107,542
Total, Unrealized Losses	(2,580)	(2,511)
Debt Securities, Held to maturity
Less than 12 months, Estimated fair value	66,985	38,199
Less than 12 months, unrealized losses	(1,411)	(1,354)
Total Estimated fair value	66,985	38,199
Total, Unrealized Losses	(1,411)	(1,354)
Municipal securities
INVESTMENT SECURITIES
Less than 12 months, Estimated Fair Value	37,869	17,529
Less than 12 months, Unrealized Losses	(606)	(555)
Total, Estimated Fair Value	37,869	17,529
Total, Unrealized Losses	(606)	(555)
Debt Securities, Held to maturity
Less than 12 months, Estimated fair value	6,343	9,882
Less than 12 months, unrealized losses	(340)	(509)
Total Estimated fair value	6,343	9,882
Total, Unrealized Losses	(340)	(509)
Agency securities
INVESTMENT SECURITIES
Less than 12 months, Estimated Fair Value	35,685	23,306
Less than 12 months, Unrealized Losses	(409)	(686)
Total, Estimated Fair Value	35,685	23,306
Total, Unrealized Losses	(409)	(686)
Debt Securities, Held to maturity
Less than 12 months, Estimated fair value	10,445	7,468
Less than 12 months, unrealized losses	(213)	(220)
Total Estimated fair value	10,445	7,468
Total, Unrealized Losses	(213)	(220)
Real estate mortgage investment conduits
INVESTMENT SECURITIES
Less than 12 months, Estimated Fair Value	36,942	25,462
Less than 12 months, Unrealized Losses	(588)	(480)
Total, Estimated Fair Value	36,942	25,462
Total, Unrealized Losses	(588)	(480)
Debt Securities, Held to maturity
Less than 12 months, Estimated fair value	17,753	9,066
Less than 12 months, unrealized losses	(264)	(141)
Total Estimated fair value	17,753	9,066
Total, Unrealized Losses	(264)	(141)
Residential mortgage-backed securities
INVESTMENT SECURITIES
Less than 12 months, Estimated Fair Value	52,675	33,164
Less than 12 months, Unrealized Losses	(671)	(614)
Total, Estimated Fair Value	52,675	33,164
Total, Unrealized Losses	(671)	(614)
Debt Securities, Held to maturity
Less than 12 months, Estimated fair value	20,547	6,035
Less than 12 months, unrealized losses	(242)	(119)
Total Estimated fair value	20,547	6,035
Total, Unrealized Losses	(242)	(119)
Other mortgage-backed securities
INVESTMENT SECURITIES
Less than 12 months, Estimated Fair Value	13,796	5,856
Less than 12 months, Unrealized Losses	(288)	(125)
12 months or longer, Estimated Fair Value	1,331	2,225
12 months or longer, Unrealized Losses	(18)	(51)
Total, Estimated Fair Value	15,127	8,081
Total, Unrealized Losses	(306)	(176)
Debt Securities, Held to maturity
Less than 12 months, Estimated fair value	11,897	5,748
Less than 12 months, unrealized losses	(352)	(365)
Total Estimated fair value	11,897	5,748
Total, Unrealized Losses	$ (352)	$ (365)

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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