INVESTMENTS - Summary of Held-To-Maturity and Available-For-Sale Investment Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Investment Holdings [Line Items]
Total	$ 88,057	$ 98,420
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	133	1,963
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(4,200)	(485)
Held-to-Maturity Market Value	83,990	99,898
Total	4,128,546	4,180,589
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	3,398	58,386
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(288,364)	(31,129)
Investment securities available-for-sale	3,843,580	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	36,723	34,961
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	0	4
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(3,343)	(189)
Investment securities available-for-sale	33,380	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	79,684	78,998
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	0	248
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(9,576)	(129)
Investment securities available-for-sale	70,108	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	697,784	728,050
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	5	6,635
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(70,037)	(10,548)
Investment securities available-for-sale	627,752	724,137
Commercial Mortgage Backed Securities [Member]
Investment Holdings [Line Items]
Total	38,327	46,362
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	0	651
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(2,541)	0
Held-to-Maturity Market Value	35,786	47,013
Total	762,091	729,948
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	3	4,294
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(31,727)	(2,352)
Investment securities available-for-sale	730,367	731,890
Collateralized Mortgage Backed Securities [Member]
Investment Holdings [Line Items]
Total	10,178	11,882
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	0	221
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(460)	0
Held-to-Maturity Market Value	9,718	12,103
Total	556,531	696,258
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	384	7,979
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(40,072)	(6,497)
Investment securities available-for-sale	516,843	697,740
Obligations of state and other political subdivisions
Investment Holdings [Line Items]
Total	8,302	8,926
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	133	915
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(123)	0
Held-to-Maturity Market Value	8,312	9,841
Total	1,070,377	1,058,735
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	2,710	35,591
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(88,243)	(8,594)
Investment securities available-for-sale	984,844	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	798,356	720,638
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	128	1,521
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(42,052)	(2,578)
Investment securities available-for-sale	756,432	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	(1,076)	(485)
Held-to-Maturity Market Value	30,174	30,941
Total	127,000	133,001
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	168	2,114
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(3,314)	(242)
Investment securities available-for-sale	$ 123,854	$ 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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