INVESTMENT SECURITIES - Fair value of impaired investment securities (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Mar. 31, 2023
INVESTMENT SECURITIES
Less than 12 months, Estimated Fair Value	$ 60,571	$ 69,746
Less than 12 months, Unrealized Losses	(1,884)	(1,500)
12 months or longer, Estimated Fair Value	142,136	134,268
12 months or longer, Unrealized Losses	(25,134)	(22,635)
Total, Estimated Fair Value	202,707	204,014
Total, Unrealized Losses	(27,018)	(24,135)
Debt Securities, Held to maturity
Less than 12 months, Estimated fair value	2	10,995
Less than 12 months, unrealized losses		(431)
12 months or longer, Estimated Fair Value	203,767	199,219
12 months or longer, Unrealized Losses	(36,084)	(33,198)
Total Estimated fair value	203,769	210,214
Total, Unrealized Losses	(36,084)	(33,629)
Municipal securities
INVESTMENT SECURITIES
Less than 12 months, Estimated Fair Value	3,388	6,277
Less than 12 months, Unrealized Losses	(122)	(133)
12 months or longer, Estimated Fair Value	35,128	32,797
12 months or longer, Unrealized Losses	(8,001)	(7,479)
Total, Estimated Fair Value	38,516	39,074
Total, Unrealized Losses	(8,123)	(7,612)
Debt Securities, Held to maturity
12 months or longer, Estimated Fair Value	7,416	7,485
12 months or longer, Unrealized Losses	(2,922)	(2,859)
Total Estimated fair value	7,416	7,485
Total, Unrealized Losses	(2,922)	(2,859)
Agency securities
INVESTMENT SECURITIES
Less than 12 months, Estimated Fair Value	43,084	43,451
Less than 12 months, Unrealized Losses	(1,096)	(747)
12 months or longer, Estimated Fair Value	42,062	36,646
12 months or longer, Unrealized Losses	(5,730)	(5,227)
Total, Estimated Fair Value	85,146	80,097
Total, Unrealized Losses	(6,826)	(5,974)
Debt Securities, Held to maturity
Less than 12 months, Estimated fair value		8,413
Less than 12 months, unrealized losses		(240)
12 months or longer, Estimated Fair Value	48,523	40,437
12 months or longer, Unrealized Losses	(5,462)	(4,851)
Total Estimated fair value	48,523	48,850
Total, Unrealized Losses	(5,462)	(5,091)
Real estate mortgage investment conduits
INVESTMENT SECURITIES
Less than 12 months, Estimated Fair Value	2,561	2,693
Less than 12 months, Unrealized Losses	(151)	(97)
12 months or longer, Estimated Fair Value	24,702	26,184
12 months or longer, Unrealized Losses	(6,059)	(5,273)
Total, Estimated Fair Value	27,263	28,877
Total, Unrealized Losses	(6,210)	(5,370)
Debt Securities, Held to maturity
Less than 12 months, Estimated fair value		2,580
Less than 12 months, unrealized losses		(191)
12 months or longer, Estimated Fair Value	28,772	27,837
12 months or longer, Unrealized Losses	(5,555)	(4,578)
Total Estimated fair value	28,772	30,417
Total, Unrealized Losses	(5,555)	(4,769)
Residential mortgage-backed securities
INVESTMENT SECURITIES
Less than 12 months, Estimated Fair Value	2,685	3,449
Less than 12 months, Unrealized Losses	(164)	(147)
12 months or longer, Estimated Fair Value	11,852	12,022
12 months or longer, Unrealized Losses	(1,037)	(894)
Total, Estimated Fair Value	14,537	15,471
Total, Unrealized Losses	(1,201)	(1,041)
Debt Securities, Held to maturity
Less than 12 months, Estimated fair value	2	2
12 months or longer, Estimated Fair Value	102,132	106,229
12 months or longer, Unrealized Losses	(18,517)	(17,542)
Total Estimated fair value	102,134	106,231
Total, Unrealized Losses	(18,517)	(17,542)
Other mortgage-backed securities
INVESTMENT SECURITIES
Less than 12 months, Estimated Fair Value	8,853	13,876
Less than 12 months, Unrealized Losses	(351)	(376)
12 months or longer, Estimated Fair Value	28,392	26,619
12 months or longer, Unrealized Losses	(4,307)	(3,762)
Total, Estimated Fair Value	37,245	40,495
Total, Unrealized Losses	(4,658)	(4,138)
Debt Securities, Held to maturity
12 months or longer, Estimated Fair Value	16,924	17,231
12 months or longer, Unrealized Losses	(3,628)	(3,368)
Total Estimated fair value	16,924	17,231
Total, Unrealized Losses	$ (3,628)	$ (3,368)