INVESTMENT SECURITIES - Schedule of Held-to-Maturity Securities with Unrealized Losses (Details) $ in Thousands	Sep. 30, 2021 USD ($)
Estimated Fair Value
Less than 12 months, estimated fair value	$ 63,304
12 months or more, estimated fair value	0
Total estimated fair value	63,304
Unrealized Losses
Less than 12 months, unrealized losses	(1,147)
12 months or more, unrealized losses	0
Total unrealized losses	(1,147)
State, county and municipal securities
Estimated Fair Value
Less than 12 months, estimated fair value	3,784
12 months or more, estimated fair value	0
Total estimated fair value	3,784
Unrealized Losses
Less than 12 months, unrealized losses	(121)
12 months or more, unrealized losses	0
Total unrealized losses	(121)
Mortgage-backed securities
Estimated Fair Value
Less than 12 months, estimated fair value	59,520
12 months or more, estimated fair value	0
Total estimated fair value	59,520
Unrealized Losses
Less than 12 months, unrealized losses	(1,026)
12 months or more, unrealized losses	0
Total unrealized losses	$ (1,026)