SECURITIES (Reconciliation of amortized cost of held to maturity securities) (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	$ 724,512	$ 740,806
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	28,007	13,428
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(342)	(971)
Debt Securities, Held-to-maturity, Allowance for Credit Loss	0
Fair Value	752,177	753,263
Debt Securities, Held-to-maturity, Amortized Cost, before Other-than-temporary Impairment	724,512	740,806
Equity Securities, FV-NI, Realized Gain (Loss)	14	18	$ 874
Internal Investment Grade [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	724,512
US Government Agencies Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	0	12,874
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain		123
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	0	0
Debt Securities, Held-to-maturity, Allowance for Credit Loss	0
Fair Value		12,997
US Treasury Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	4,017	4,032
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	60	21
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	0	0
Debt Securities, Held-to-maturity, Allowance for Credit Loss	0
Fair Value	4,077	4,053
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	356,085	397,414
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	18,036	8,445
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	0	(57)
Debt Securities, Held-to-maturity, Allowance for Credit Loss	0
Fair Value	374,121	405,802
Agency collateralized mortgage obligations [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	335,993	293,662
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	8,466	4,501
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(340)	(849)
Debt Securities, Held-to-maturity, Allowance for Credit Loss	0
Fair Value	344,119	297,314
Single issuer trust preferred securities issued by banks [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	1,500	1,500
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	0	0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(2)	(10)
Debt Securities, Held-to-maturity, Allowance for Credit Loss	0
Fair Value	1,498	1,490
Small Business Administration Pooled Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	26,917	31,324
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	1,445	338
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	0	(55)
Debt Securities, Held-to-maturity, Allowance for Credit Loss	0
Fair Value	$ 28,362	$ 31,607

Amount of allowance for credit loss for debt security measured at amortized cost (held-to-maturity).

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