INVESTMENT SECURITIES - Amortized Cost and Approximate Fair Value of Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Available for sale securities
Amortized Cost	$ 2,376,492	$ 2,268,655
Gross Unrealized Gains	94	89,536
Gross Unrealized Losses	392,614	13,640
Fair Value	1,983,972	2,344,551
Held to maturity securities
Amortized Cost	2,311,041	2,180,047
Allowance for Credit Losses	245	245
Net Carrying Amount	2,310,796	2,179,802
Gross Unrealized Gains	113	37,776
Gross Unrealized Losses	444,066	15,320
Fair Value	1,867,088	2,202,503
U.S. Treasury
Available for sale securities
Amortized Cost	2,107	1,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	40	1
Fair Value	2,067	999
U.S. Government-sponsored agency securities
Available for sale securities
Amortized Cost	121,907	96,244
Gross Unrealized Gains	0	437
Gross Unrealized Losses	16,141	1,545
Fair Value	105,766	95,136
Held to maturity securities
Amortized Cost	399,089	371,457
Allowance for Credit Losses	0	0
Net Carrying Amount	399,089	371,457
Gross Unrealized Gains	0	226
Gross Unrealized Losses	66,514	7,268
Fair Value	332,575	364,415
State and municipal
Available for sale securities
Amortized Cost	1,611,859	1,495,696
Gross Unrealized Gains	93	81,734
Gross Unrealized Losses	266,996	898
Fair Value	1,344,956	1,576,532
Held to maturity securities
Amortized Cost	1,114,312	1,057,301
Allowance for Credit Losses	245	245
Net Carrying Amount	1,114,067	1,057,056
Gross Unrealized Gains	113	29,593
Gross Unrealized Losses	256,834	2,170
Fair Value	857,591	1,084,724
U.S. Government-sponsored mortgage-backed securities
Available for sale securities
Amortized Cost	627,583	671,684
Gross Unrealized Gains	1	7,109
Gross Unrealized Losses	108,795	11,188
Fair Value	518,789	667,605
Held to maturity securities
Amortized Cost	796,140	749,789
Allowance for Credit Losses	0	0
Net Carrying Amount	796,140	749,789
Gross Unrealized Gains	0	7,957
Gross Unrealized Losses	120,709	5,881
Fair Value	675,431	751,865
Corporate obligations
Available for sale securities
Amortized Cost	13,036	4,031
Gross Unrealized Gains	0	256
Gross Unrealized Losses	642	8
Fair Value	12,394	4,279
Foreign investment
Held to maturity securities
Amortized Cost	1,500	1,500
Allowance for Credit Losses	0	0
Net Carrying Amount	1,500	1,500
Gross Unrealized Gains	0	0
Gross Unrealized Losses	9	1
Fair Value	$ 1,491	$ 1,499

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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Amount, before tax, of unrealized loss 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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