INVESTMENT SECURITIES - Fair value of impaired investment securities (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Mar. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, Estimated Fair Value	$ 120,190	$ 105,317
Less than 12 months, Unrealized Losses	(1,370)	(2,460)
12 months or longer, Estimated Fair Value	1,993	2,225
12 months or longer, Unrealized Losses	(44)	(51)
Total, Estimated Fair Value	122,183	107,542
Total, Unrealized Losses	(1,414)	(2,511)
Debt Securities, Held to maturity
Less than 12 months, Estimated fair value	34,912	38,199
Less than 12 months, unrealized losses	(597)	(1,354)
Total Estimated fair value	34,912	38,199
Total, Unrealized Losses	(597)	(1,354)
Municipal securities
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, Estimated Fair Value	12,971	17,529
Less than 12 months, Unrealized Losses	(213)	(555)
Total, Estimated Fair Value	12,971	17,529
Total, Unrealized Losses	(213)	(555)
Debt Securities, Held to maturity
Less than 12 months, Estimated fair value	6,511	9,882
Less than 12 months, unrealized losses	(177)	(509)
Total Estimated fair value	6,511	9,882
Total, Unrealized Losses	(177)	(509)
Agency securities
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, Estimated Fair Value	20,577	23,306
Less than 12 months, Unrealized Losses	(392)	(686)
Total, Estimated Fair Value	20,577	23,306
Total, Unrealized Losses	(392)	(686)
Debt Securities, Held to maturity
Less than 12 months, Estimated fair value	7,570	7,468
Less than 12 months, unrealized losses	(105)	(220)
Total Estimated fair value	7,570	7,468
Total, Unrealized Losses	(105)	(220)
Real estate mortgage investment conduits
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, Estimated Fair Value	38,492	25,462
Less than 12 months, Unrealized Losses	(411)	(480)
Total, Estimated Fair Value	38,492	25,462
Total, Unrealized Losses	(411)	(480)
Debt Securities, Held to maturity
Less than 12 months, Estimated fair value	8,991	9,066
Less than 12 months, unrealized losses	(77)	(141)
Total Estimated fair value	8,991	9,066
Total, Unrealized Losses	(77)	(141)
Residential mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, Estimated Fair Value	45,122	33,164
Less than 12 months, Unrealized Losses	(349)	(614)
Total, Estimated Fair Value	45,122	33,164
Total, Unrealized Losses	(349)	(614)
Debt Securities, Held to maturity
Less than 12 months, Estimated fair value	5,895	6,035
Less than 12 months, unrealized losses	(75)	(119)
Total Estimated fair value	5,895	6,035
Total, Unrealized Losses	(75)	(119)
Other mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, Estimated Fair Value	3,028	5,856
Less than 12 months, Unrealized Losses	(5)	(125)
12 months or longer, Estimated Fair Value	1,993	2,225
12 months or longer, Unrealized Losses	(44)	(51)
Total, Estimated Fair Value	5,021	8,081
Total, Unrealized Losses	(49)	(176)
Debt Securities, Held to maturity
Less than 12 months, Estimated fair value	5,945	5,748
Less than 12 months, unrealized losses	(163)	(365)
Total Estimated fair value	5,945	5,748
Total, Unrealized Losses	$ (163)	$ (365)