INVESTMENT SECURITIES - Available-for-Sale Portfolio (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020
Available-for-Sale Portfolio [Abstract]
Amortized cost	$ 4,980,102	$ 3,427,779
Gross unrealized gains	65,387	136,901
Gross unrealized losses	111,279	16,788
Fair value	4,934,210	3,547,892
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized cost	4,980,102
Debt Securities, Available-for-sale	4,934,210
U.S. Treasury and Agency Securities
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized cost	4,064,624	2,423,236
Gross unrealized gains	39,997	94,741
Gross unrealized losses	106,057	16,595
Debt Securities, Available-for-sale	3,998,564	2,501,382
Obligations of State and Political Subdivisions
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized cost	413,019	451,028
Gross unrealized gains	17,326	24,632
Gross unrealized losses	56	0
Debt Securities, Available-for-sale	430,289	475,660
Government Agency Mortgage-Backed Securities
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized cost	474,506	506,540
Gross unrealized gains	7,615	16,280
Gross unrealized losses	5,065	182
Debt Securities, Available-for-sale	477,056	522,638
Corporate debt securities
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized cost	8,000	4,499
Gross unrealized gains	39	137
Gross unrealized losses	77	1
Debt Securities, Available-for-sale	7,962	4,635
Government Agency Collateralized Mortgage Obligations
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized cost	19,953	42,476
Gross unrealized gains	410	1,111
Gross unrealized losses	24	10
Debt Securities, Available-for-sale	20,339	43,577
Federal Reserve Bank Stock [Member]
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Gross unrealized losses	0	0
Other Equity Securities [Member]
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Gross unrealized losses	0	0
Federal Home Loan Bank Common Stock [Member]
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Gross unrealized losses	$ 0	$ 0

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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-Publisher FASB
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-Section 50
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-Subparagraph (b)
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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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Amortized cost of 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 of 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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