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INVESTMENT SECURITIES - Investment Securities in a Continuous Unrealized Loss Position (Details) $ in Thousands | Dec. 31, 2021 USD ($) position | Dec. 31, 2020 USD ($) position
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Available-for-Sale Securities in Unrealized Loss Positions, Number of Positions [Abstract] |  |
Less than 12 months | position | 240 | 117
12 months or longer | position | 66 | 3
Total | position | 306 | 120
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value [Abstract] |  |
Less than 12 months | $ 1,395,578 | $ 913,612
12 months or longer | 967,788 | 14
Total | 2,363,366 | 913,626
Available-for-Sale Securities, in Unrealized Loss Position, Gross Unrealized Losses [Abstract] |  |
Less than 12 months | 17,505 | 16,788
12 months or longer | 93,774 | 0
Total | 111,279 | 16,788
Available-for-sale, allowance for credit losses | $ 0 | $ 0
U.S. Treasury and Agency Securities |  |
Available-for-Sale Securities in Unrealized Loss Positions, Number of Positions [Abstract] |  |
Less than 12 months | 47 | 13
12 months or longer | position | 13 | 0
Total | position | 60 | 13
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value [Abstract] |  |
Less than 12 months |  | $ 831,015
12 months or longer | $ 900,462 | 0
Total | 2,124,563 | 831,015
Available-for-Sale Securities, in Unrealized Loss Position, Gross Unrealized Losses [Abstract] |  |
Less than 12 months | 14,873 | 16,595
12 months or longer | 91,184 | 0
Total | $ 106,057 | $ 16,595
Obligations of State and Political Subdivisions |  |
Available-for-Sale Securities in Unrealized Loss Positions, Number of Positions [Abstract] |  |
Less than 12 months | 27 | 1
12 months or longer | position | 0 | 0
Total | position | 27 | 1
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value [Abstract] |  |
Less than 12 months |  | $ 358
12 months or longer | $ 0 | 0
Total | 23,966 | 358
Available-for-Sale Securities, in Unrealized Loss Position, Gross Unrealized Losses [Abstract] |  |
Less than 12 months | 56 | 0
12 months or longer | 0 | 0
Total | $ 56 | $ 0
Government Agency Mortgage-Backed Securities |  |
Available-for-Sale Securities in Unrealized Loss Positions, Number of Positions [Abstract] |  |
Less than 12 months | 147 | 89
12 months or longer | position | 52 | 2
Total | position | 199 | 91
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value [Abstract] |  |
Less than 12 months |  | $ 75,992
12 months or longer | $ 67,273 | 14
Total | 206,715 | 76,006
Available-for-Sale Securities, in Unrealized Loss Position, Gross Unrealized Losses [Abstract] |  |
Less than 12 months | 2,475 | 182
12 months or longer | 2,590 | 0
Total | $ 5,065 | $ 182
Corporate debt securities |  |
Available-for-Sale Securities in Unrealized Loss Positions, Number of Positions [Abstract] |  |
Less than 12 months | 1 | 1
12 months or longer | position | 0 | 0
Total | position | 1 | 1
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value [Abstract] |  |
Less than 12 months |  | $ 1,001
12 months or longer | $ 0 | 0
Total | 4,923 | 1,001
Available-for-Sale Securities, in Unrealized Loss Position, Gross Unrealized Losses [Abstract] |  |
Less than 12 months | 77 | 1
12 months or longer | 0 | 0
Total | $ 77 | $ 1
Government Agency Collateralized Mortgage Obligations |  |
Available-for-Sale Securities in Unrealized Loss Positions, Number of Positions [Abstract] |  |
Less than 12 months | 18 | 13
12 months or longer | position | 1 | 1
Total | position | 19 | 14
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value [Abstract] |  |
Less than 12 months |  | $ 5,246
12 months or longer | $ 53 | 0
Total | 3,199 | 5,246
Available-for-Sale Securities, in Unrealized Loss Position, Gross Unrealized Losses [Abstract] |  |
Less than 12 months | 24 | 10
12 months or longer | 0 | 0
Total | $ 24 | $ 10

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- Definition Amount of allowance for credit loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 50 -Paragraph 9 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=124269663&loc=SL82922900-210455 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 50 -Paragraph 9 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=124269663&loc=SL82922900-210455 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (aaa) -URI http://asc.fasb.org/extlink&oid=123581744&loc=d3e27161-111563 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=124258926&loc=SL82898722-210454 + Details
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