BUSINESS COMBINATIONS - Schedule of Changes to Goodwill Subsequent to Acquisition (Details) $ in Thousands	6 Months Ended
Sep. 30, 2019 USD ($)
Goodwill [Roll Forward]
Goodwill ending balance	$ 472,958
Beneficial
Goodwill [Roll Forward]
Goodwill beginning balance	309,486
Goodwill ending balance	306,951
Deposits \| Beneficial
Goodwill [Roll Forward]
Goodwill, purchase accounting adjustments	790
Deferred income taxes \| Beneficial
Goodwill [Roll Forward]
Goodwill, purchase accounting adjustments	985
Investment securities \| Beneficial
Goodwill [Roll Forward]
Goodwill, purchase accounting adjustments	(3,150)
Cash \| Beneficial
Goodwill [Roll Forward]
Goodwill, purchase accounting adjustments	246
Loans \| Beneficial
Goodwill [Roll Forward]
Goodwill, purchase accounting adjustments	911
Premises and equipment \| Beneficial
Goodwill [Roll Forward]
Goodwill, purchase accounting adjustments	(741)
Other assets \| Beneficial
Goodwill [Roll Forward]
Goodwill, purchase accounting adjustments	(418)
Other liabilities \| Beneficial
Goodwill [Roll Forward]
Goodwill, purchase accounting adjustments	$ (1,158)

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=77989000&loc=SL49117168-202975

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=99380562&loc=d3e13770-109266

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Amount of increase (decrease) from adjustments after acquisition date under purchase accounting of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 25
-Paragraph 16
-URI http://asc.fasb.org/extlink&oid=116868678&loc=d3e961-128460

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=108376223&loc=d3e13816-109267

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