INCOME TAXES - Summary of Income Tax Expense (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
INCOME TAXES
Current federal									$ 20,032	$ 19,430	$ 16,871
Deferred federal									(1,688)	(408)	707
Revalue deferred taxes due to tax reform											(408)
Current state									1,484	1,394	1,462
Deferred state									(289)	(78)	(99)
Total income tax expense	$ 6,071	$ 5,377	$ 4,448	$ 3,643	$ 5,431	$ 5,119	$ 5,409	$ 4,379	$ 19,539	$ 20,338	$ 18,533