INVESTMENT SECURITIES - Fair value of impaired investment securities (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Mar. 31, 2022
INVESTMENT SECURITIES
Less than 12 months, Estimated Fair Value	$ 110,470	$ 120,499
Less than 12 months, Unrealized Losses	(6,041)	(9,798)
12 months or longer, Estimated Fair Value	98,285	35,740
12 months or longer, Unrealized Losses	(22,352)	(3,351)
Total, Estimated Fair Value	208,755	156,239
Total, Unrealized Losses	(28,393)	(13,149)
Debt Securities, Held to maturity
Less than 12 months, Estimated fair value	69,597	192,642
Less than 12 months, unrealized losses	(8,168)	(12,552)
12 months or longer, Estimated Fair Value	140,136	40,417
12 months or longer, Unrealized Losses	(29,246)	(4,519)
Total Estimated fair value	209,733	233,059
Total, Unrealized Losses	(37,414)	(17,071)
Municipal securities
INVESTMENT SECURITIES
Less than 12 months, Estimated Fair Value	14,341	32,767
Less than 12 months, Unrealized Losses	(2,024)	(4,293)
12 months or longer, Estimated Fair Value	22,996	3,282
12 months or longer, Unrealized Losses	(7,372)	(221)
Total, Estimated Fair Value	37,337	36,049
Total, Unrealized Losses	(9,396)	(4,514)
Debt Securities, Held to maturity
Less than 12 months, Estimated fair value	1,649	5,911
Less than 12 months, unrealized losses	(777)	(816)
12 months or longer, Estimated Fair Value	5,457	3,036
12 months or longer, Unrealized Losses	(2,467)	(606)
Total Estimated fair value	7,106	8,947
Total, Unrealized Losses	(3,244)	(1,422)
Agency securities
INVESTMENT SECURITIES
Less than 12 months, Estimated Fair Value	50,832	22,288
Less than 12 months, Unrealized Losses	(1,047)	(1,565)
12 months or longer, Estimated Fair Value	35,829	16,414
12 months or longer, Unrealized Losses	(6,037)	(1,579)
Total, Estimated Fair Value	86,661	38,702
Total, Unrealized Losses	(7,084)	(3,144)
Debt Securities, Held to maturity
Less than 12 months, Estimated fair value	20,800	35,930
Less than 12 months, unrealized losses	(1,473)	(1,708)
12 months or longer, Estimated Fair Value	27,209	6,897
12 months or longer, Unrealized Losses	(4,414)	(742)
Total Estimated fair value	48,009	42,827
Total, Unrealized Losses	(5,887)	(2,450)
Real estate mortgage investment conduits
INVESTMENT SECURITIES
Less than 12 months, Estimated Fair Value	5,903	17,334
Less than 12 months, Unrealized Losses	(462)	(1,310)
12 months or longer, Estimated Fair Value	23,005	15,275
12 months or longer, Unrealized Losses	(5,579)	(1,537)
Total, Estimated Fair Value	28,908	32,609
Total, Unrealized Losses	(6,041)	(2,847)
Debt Securities, Held to maturity
Less than 12 months, Estimated fair value	12,891	26,233
Less than 12 months, unrealized losses	(1,517)	(1,715)
12 months or longer, Estimated Fair Value	17,771	7,735
12 months or longer, Unrealized Losses	(3,829)	(742)
Total Estimated fair value	30,662	33,968
Total, Unrealized Losses	(5,346)	(2,457)
Residential mortgage-backed securities
INVESTMENT SECURITIES
Less than 12 months, Estimated Fair Value	13,985	15,702
Less than 12 months, Unrealized Losses	(968)	(436)
12 months or longer, Estimated Fair Value	2,071
12 months or longer, Unrealized Losses	(248)
Total, Estimated Fair Value	16,056	15,702
Total, Unrealized Losses	(1,216)	(436)
Debt Securities, Held to maturity
Less than 12 months, Estimated fair value	28,800	111,096
Less than 12 months, unrealized losses	(3,641)	(7,160)
12 months or longer, Estimated Fair Value	78,217	17,363
12 months or longer, Unrealized Losses	(15,613)	(1,723)
Total Estimated fair value	107,017	128,459
Total, Unrealized Losses	(19,254)	(8,883)
Other mortgage-backed securities
INVESTMENT SECURITIES
Less than 12 months, Estimated Fair Value	25,409	32,408
Less than 12 months, Unrealized Losses	(1,540)	(2,194)
12 months or longer, Estimated Fair Value	14,384	769
12 months or longer, Unrealized Losses	(3,116)	(14)
Total, Estimated Fair Value	39,793	33,177
Total, Unrealized Losses	(4,656)	(2,208)
Debt Securities, Held to maturity
Less than 12 months, Estimated fair value	5,457	13,472
Less than 12 months, unrealized losses	(760)	(1,153)
12 months or longer, Estimated Fair Value	11,482	5,386
12 months or longer, Unrealized Losses	(2,923)	(706)
Total Estimated fair value	16,939	18,858
Total, Unrealized Losses	$ (3,683)	$ (1,859)