INVESTMENT SECURITIES - Summary of Unrealized Losses - Available-for-Sale (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, fair value	$ 31,586	$ 90,976
Less than 12 months, unrealized loss	1,328	787
12 months or more, fair value	216,575	158,412
12 months or more, unrealized loss	6,641	4,528
Total, fair value	248,161	249,388
Total, unrealized loss	7,969	5,315
State, county, and municipal securities
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, fair value	2,573	596
Less than 12 months, unrealized loss	11	5
12 months or more, fair value	19,539	12,716
12 months or more, unrealized loss	754	437
Total, fair value	22,112	13,312
Total, unrealized loss	765	442
Mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, fair value	25,706	87,390
Less than 12 months, unrealized loss	34	772
12 months or more, fair value	197,036	145,696
12 months or more, unrealized loss	5,887	4,091
Total, fair value	222,742	233,086
Total, unrealized loss	5,921	4,863
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, fair value	3,307	2,990
Less than 12 months, unrealized loss	1,283	10
12 months or more, fair value	0	0
12 months or more, unrealized loss	0	0
Total, fair value	3,307	2,990
Total, unrealized loss	$ 1,283	$ 10