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DERIVATIVE FINANCIAL INSTRUMENTS AND HEDGING ACTIVITIES - Narrative (Details)	9 Months Ended
	Sep. 30, 2022 USD ($) instrument	Dec. 31, 2021 USD ($)
Derivative [Line Items]
Notional amount	$ 4,043,682,000	$ 3,711,905,000
Cash collateral pledged	14,900,000
Amortized cost of securities pledged as collateral to derivative counterparties	22,500,000
Fair value of securities as pledged collateral to derivative counterparties	22,300,000
Commercial counterparties
Derivative [Line Items]
Net asset position	52,800,000	2,200,000
Interest rate swaps
Derivative [Line Items]
Notional amount	7,300,000
Cash collateral pledged	$ 14,863,000	43,694,000
Interest rate swaps | Minimum
Derivative [Line Items]
Derivative, term	2 years
Interest rate swaps | Maximum
Derivative [Line Items]
Derivative, term	3 years
Interest rate swaps | Commercial counterparties
Derivative [Line Items]
Cash collateral pledged	$ 0	0
Net asset position	98,000	76,800,000
Collateral already posted, aggregate fair value	95,900,000	2,500,000
Interest rate swaps | Institutional counterparties
Derivative [Line Items]
Cash collateral pledged	14,863,000	43,694,000
Collateral already posted, aggregate fair value	190,000	33,300,000
Non-hedging derivatives:
Derivative [Line Items]
Notional amount	3,132,000	8,192,000
Economic hedges
Derivative [Line Items]
Credit valuation adjustments	$ 0
Economic hedges | Interest rate swap on tax advantaged economic development bond
Derivative [Line Items]
Fixed rate of interest	5.09%
Maturity period	21 years
Economic hedges | Economic hedges:
Derivative [Line Items]
Notional amount	$ 3,640,550,000	3,703,713,000
Economic hedges | Economic hedges: | Interest rate swaps
Derivative [Line Items]
Notional amount	3,300,000,000
Economic hedges | Economic hedges: | Interest rate swaps | Commercial loan
Derivative [Line Items]
Notional amount	1,653,839,000	1,684,238,000
Economic hedges | Economic hedges: | Risk participation agreements with dealer banks
Derivative [Line Items]
Notional amount	325,063,000	$ 320,981,000
Economic hedges | Economic hedges: | Forward sale commitments
Derivative [Line Items]
Notional amount	1,000,000
Cash flow hedges:
Derivative [Line Items]
Notional amount	$ 400,000,000
Cash flow hedges: | Interest rate swaps
Derivative [Line Items]
Number of instruments | instrument	3
Cash flow hedges: | Interest rate swaps | Commercial loan
Derivative [Line Items]
Notional amount	$ 225,000,000
Cash flow hedges: | Forward Starting Interest Rate Swaps
Derivative [Line Items]
Number of instruments | instrument	3
Cash flow hedges: | Forward Starting Interest Rate Swaps | Commercial loan
Derivative [Line Items]
Notional amount	$ 175,000,000
Cash flow hedges: | Economic hedges: | Interest rate swaps
Derivative [Line Items]
Notional amount	$ 400,000,000

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Fixed interest rate related to the interest rate derivative.

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