INVESTMENT SECURITIES - Fair value of impaired investment securities (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Mar. 31, 2022
INVESTMENT SECURITIES
Less than 12 months, Estimated Fair Value	$ 69,746	$ 120,499
Less than 12 months, Unrealized Losses	(1,500)	(9,798)
12 months or longer, Estimated Fair Value	134,268	35,740
12 months or longer, Unrealized Losses	(22,635)	(3,351)
Total, Estimated Fair Value	204,014	156,239
Total, Unrealized Losses	(24,135)	(13,149)
Debt Securities, Held to maturity
Less than 12 months, Estimated fair value	10,995	192,642
Less than 12 months, unrealized losses	(431)	(12,552)
12 months or longer, Estimated Fair Value	199,219	40,417
12 months or longer, Unrealized Losses	(33,198)	(4,519)
Total Estimated fair value	210,214	233,059
Total, Unrealized Losses	(33,629)	(17,071)
Municipal securities
INVESTMENT SECURITIES
Less than 12 months, Estimated Fair Value	6,277	32,767
Less than 12 months, Unrealized Losses	(133)	(4,293)
12 months or longer, Estimated Fair Value	32,797	3,282
12 months or longer, Unrealized Losses	(7,479)	(221)
Total, Estimated Fair Value	39,074	36,049
Total, Unrealized Losses	(7,612)	(4,514)
Debt Securities, Held to maturity
Less than 12 months, Estimated fair value		5,911
Less than 12 months, unrealized losses		(816)
12 months or longer, Estimated Fair Value	7,485	3,036
12 months or longer, Unrealized Losses	(2,859)	(606)
Total Estimated fair value	7,485	8,947
Total, Unrealized Losses	(2,859)	(1,422)
Agency securities
INVESTMENT SECURITIES
Less than 12 months, Estimated Fair Value	43,451	22,288
Less than 12 months, Unrealized Losses	(747)	(1,565)
12 months or longer, Estimated Fair Value	36,646	16,414
12 months or longer, Unrealized Losses	(5,227)	(1,579)
Total, Estimated Fair Value	80,097	38,702
Total, Unrealized Losses	(5,974)	(3,144)
Debt Securities, Held to maturity
Less than 12 months, Estimated fair value	8,413	35,930
Less than 12 months, unrealized losses	(240)	(1,708)
12 months or longer, Estimated Fair Value	40,437	6,897
12 months or longer, Unrealized Losses	(4,851)	(742)
Total Estimated fair value	48,850	42,827
Total, Unrealized Losses	(5,091)	(2,450)
Real estate mortgage investment conduits
INVESTMENT SECURITIES
Less than 12 months, Estimated Fair Value	2,693	17,334
Less than 12 months, Unrealized Losses	(97)	(1,310)
12 months or longer, Estimated Fair Value	26,184	15,275
12 months or longer, Unrealized Losses	(5,273)	(1,537)
Total, Estimated Fair Value	28,877	32,609
Total, Unrealized Losses	(5,370)	(2,847)
Debt Securities, Held to maturity
Less than 12 months, Estimated fair value	2,580	26,233
Less than 12 months, unrealized losses	(191)	(1,715)
12 months or longer, Estimated Fair Value	27,837	7,735
12 months or longer, Unrealized Losses	(4,578)	(742)
Total Estimated fair value	30,417	33,968
Total, Unrealized Losses	(4,769)	(2,457)
Residential mortgage-backed securities
INVESTMENT SECURITIES
Less than 12 months, Estimated Fair Value	3,449	15,702
Less than 12 months, Unrealized Losses	(147)	(436)
12 months or longer, Estimated Fair Value	12,022
12 months or longer, Unrealized Losses	(894)
Total, Estimated Fair Value	15,471	15,702
Total, Unrealized Losses	(1,041)	(436)
Debt Securities, Held to maturity
Less than 12 months, Estimated fair value	2	111,096
Less than 12 months, unrealized losses		(7,160)
12 months or longer, Estimated Fair Value	106,229	17,363
12 months or longer, Unrealized Losses	(17,542)	(1,723)
Total Estimated fair value	106,231	128,459
Total, Unrealized Losses	(17,542)	(8,883)
Other mortgage-backed securities
INVESTMENT SECURITIES
Less than 12 months, Estimated Fair Value	13,876	32,408
Less than 12 months, Unrealized Losses	(376)	(2,194)
12 months or longer, Estimated Fair Value	26,619	769
12 months or longer, Unrealized Losses	(3,762)	(14)
Total, Estimated Fair Value	40,495	33,177
Total, Unrealized Losses	(4,138)	(2,208)
Debt Securities, Held to maturity
Less than 12 months, Estimated fair value		13,472
Less than 12 months, unrealized losses		(1,153)
12 months or longer, Estimated Fair Value	17,231	5,386
12 months or longer, Unrealized Losses	(3,368)	(706)
Total Estimated fair value	17,231	18,858
Total, Unrealized Losses	$ (3,368)	$ (1,859)