INVESTMENTS - Summary of Held-To-Maturity and Available-For-Sale Investment Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Investment Holdings [Line Items]
Total	$ 92,597	$ 98,420
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	317	1,963
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(2,913)	(485)
Held-to-Maturity Market Value	90,001	99,898
Total	4,113,169	4,180,589
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	13,747	58,386
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(169,034)	(31,129)
Investment securities available-for-sale	3,957,882	4,207,846
U.S. Treasuries
Investment Holdings [Line Items]
Total	0	0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	0	0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	0	0
Held-to-Maturity Market Value	0	0
Total	34,967	34,961
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	1	4
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(2,244)	(189)
Investment securities available-for-sale	32,724	34,776
Securities of U.S. government agencies and corporations
Investment Holdings [Line Items]
Total	0	0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	0	0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	0	0
Held-to-Maturity Market Value	0	0
Total	79,338	78,998
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	0	248
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(5,665)	(129)
Investment securities available-for-sale	73,673	79,117
Residential Mortgage Backed Securities [Member]
Investment Holdings [Line Items]
Total	0	0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	0	0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	0	0
Held-to-Maturity Market Value	0	0
Total	709,888	728,050
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	602	6,635
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(43,418)	(10,548)
Investment securities available-for-sale	667,072	724,137
Commercial Mortgage Backed Securities [Member]
Investment Holdings [Line Items]
Total	42,211	46,362
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	0	651
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(1,403)	0
Held-to-Maturity Market Value	40,808	47,013
Total	754,978	729,948
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	355	4,294
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(17,903)	(2,352)
Investment securities available-for-sale	737,430	731,890
Collateralized Mortgage Backed Securities [Member]
Investment Holdings [Line Items]
Total	10,780	11,882
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	0	221
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(287)	0
Held-to-Maturity Market Value	10,493	12,103
Total	621,240	696,258
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	1,277	7,979
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(27,662)	(6,497)
Investment securities available-for-sale	594,855	697,740
Obligations of state and other political subdivisions
Investment Holdings [Line Items]
Total	8,356	8,926
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	317	915
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	0	0
Held-to-Maturity Market Value	8,673	9,841
Total	1,071,171	1,058,735
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	10,441	35,591
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(49,260)	(8,594)
Investment securities available-for-sale	1,032,352	1,085,732
Asset-backed Securities [Member]
Investment Holdings [Line Items]
Total	0	0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	0	0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	0	0
Held-to-Maturity Market Value	0	0
Total	713,587	720,638
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	361	1,521
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(21,321)	(2,578)
Investment securities available-for-sale	692,627	719,581
Other securities
Investment Holdings [Line Items]
Total	31,250	31,250
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	0	176
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(1,223)	(485)
Held-to-Maturity Market Value	30,027	30,941
Total	128,000	133,001
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	710	2,114
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(1,561)	(242)
Investment securities available-for-sale	$ 127,149	$ 134,873

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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