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INVESTMENT SECURITIES - Fair value of impaired investment securities (Details) - USD ($) $ in Thousands | Sep. 30, 2020 | Mar. 31, 2020
--- | --- | ---
Debt Securities, Available-for-sale [Line Items] |  |
Less than 12 months, Estimated Fair Value | $ 31 | $ 16,233
Less than 12 months, Unrealized Losses |  | (90)
12 months or longer, Estimated Fair Value | 6,534 | 5,320
12 months or longer, Unrealized Losses | (90) | (101)
Total, Estimated Fair Value | 6,565 | 21,553
Total, Unrealized Losses | (90) | (191)
Agency securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Less than 12 months, Estimated Fair Value |  | 1,998
Less than 12 months, Unrealized Losses |  | (10)
12 months or longer, Estimated Fair Value | 1,998 |
12 months or longer, Unrealized Losses | (8) |
Total, Estimated Fair Value | 1,998 | 1,998
Total, Unrealized Losses | (8) | (10)
Real estate mortgage investment conduits |  |
Debt Securities, Available-for-sale [Line Items] |  |
Less than 12 months, Estimated Fair Value | 31 |
Total, Estimated Fair Value | 31 |
Residential mortgage-backed securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Less than 12 months, Estimated Fair Value |  | 2,509
Less than 12 months, Unrealized Losses |  | (22)
12 months or longer, Estimated Fair Value |  | 409
12 months or longer, Unrealized Losses |  | (8)
Total, Estimated Fair Value |  | 2,918
Total, Unrealized Losses |  | (30)
Other mortgage-backed securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Less than 12 months, Estimated Fair Value |  | 11,726
Less than 12 months, Unrealized Losses |  | (58)
12 months or longer, Estimated Fair Value | 4,536 | 4,911
12 months or longer, Unrealized Losses | (82) | (93)
Total, Estimated Fair Value | 4,536 | 16,637
Total, Unrealized Losses | $ (82) | $ (151)

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- Definition Amount of accumulated unrealized loss on 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 12 months or longer, without allowance for credit loss. Includes beneficial interest in securitized financial asset. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27337-111563 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=121582814&loc=SL82922890-210455 + Details
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- Definition Amount of accumulated unrealized loss on 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 less than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=121582814&loc=SL82922890-210455 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27337-111563 + Details
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