SECURITIES - Securities Available for Sale (Details) - USD ($)	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Amortized cost and estimated fair value of securities available for sale [Abstract]
Amortized Cost	$ 627,578,000		$ 542,362,000
Unrealized Gains	8,055,000		12,654,000
Unrealized Losses	9,438,000		405,000
Estimated Fair Value	626,195,000		554,611,000
Amortized Cost [Abstract]
Within one year	610,000
After one, but within five years	31,385,000
After five, but within ten years	17,487,000
After ten years	758,000
Total	50,240,000
Amortized Cost	627,578,000		542,362,000
Fair Value [Abstract]
Within one year	611,000
After one, but within five years	32,858,000
After five, but within ten years	18,234,000
After ten years	806,000
Total	52,509,000
Fair value	626,195,000		554,611,000
Debt Securities, Available-for-sale, Realized Gain (Loss) [Abstract]
Proceeds form sale of securities resulting in gain (loss)	0	$ 0
Obligations of U.S. Government and U.S. Government sponsored enterprises
Amortized cost and estimated fair value of securities available for sale [Abstract]
Amortized Cost	610,000
Unrealized Gains	1,000
Unrealized Losses	0
Estimated Fair Value	611,000
Amortized Cost [Abstract]
Amortized Cost	610,000
Fair Value [Abstract]
Fair value	611,000
Mortgage-backed securities, residential
Amortized cost and estimated fair value of securities available for sale [Abstract]
Amortized Cost	523,974,000		458,245,000
Unrealized Gains	5,698,000		9,822,000
Unrealized Losses	9,175,000		201,000
Estimated Fair Value	520,497,000		467,866,000
Amortized Cost [Abstract]
Without single maturity date	523,974,000
Amortized Cost	523,974,000		458,245,000
Fair Value [Abstract]
Without single maturity date	520,497,000
Fair value	520,497,000		467,866,000
Obligations of states and political subdivisions
Amortized cost and estimated fair value of securities available for sale [Abstract]
Amortized Cost	40,630,000		40,662,000
Unrealized Gains	2,192,000		2,743,000
Unrealized Losses	0		0
Estimated Fair Value	42,822,000		43,405,000
Amortized Cost [Abstract]
Amortized Cost	40,630,000		40,662,000
Fair Value [Abstract]
Fair value	42,822,000		43,405,000
Corporate bonds and notes
Amortized cost and estimated fair value of securities available for sale [Abstract]
Amortized Cost	9,000,000		9,000,000
Unrealized Gains	112,000		47,000
Unrealized Losses	36,000		12,000
Estimated Fair Value	9,076,000		9,035,000
Amortized Cost [Abstract]
Amortized Cost	9,000,000		9,000,000
Fair Value [Abstract]
Fair value	9,076,000		9,035,000
SBA loan pools
Amortized cost and estimated fair value of securities available for sale [Abstract]
Amortized Cost	53,364,000		34,455,000
Unrealized Gains	52,000		42,000
Unrealized Losses	227,000		192,000
Estimated Fair Value	53,189,000		34,305,000
Amortized Cost [Abstract]
Without single maturity date	53,364,000
Amortized Cost	53,364,000		34,455,000
Fair Value [Abstract]
Without single maturity date	53,189,000
Fair value	$ 53,189,000		$ 34,305,000

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).

Name:	us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

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).