FAIR VALUE - Summary of carrying amounts and estimated fair values for financial instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Assets
Cash and cash equivalents	$ 118,514	$ 78,638	$ 69,766	$ 73,357
Fair Value	52,500	58,903
Loans, net	1,035,709	990,132
Mortgage loans held for sale	64,120	48,312
Accrued interest receivable	3,107	3,048
Other assets	24,297	16,544
Liabilities
Deposits	1,178,450	1,086,784
FHLB Topeka Borrowings – fixed rate	10,000	10,000
Subordinated notes	14,459	6,560
Accrued interest payable	417	299
Carrying Amount
Assets
Cash and cash equivalents	118,514	78,638
Fair Value	52,500	58,903
Loans, net	1,035,709	990,132
Mortgage loans held for sale	64,120	48,312
Accrued interest receivable	3,107	3,048
Other assets	726	713
Liabilities
Deposits	1,178,450	1,086,784
FHLB Topeka Borrowings – fixed rate	10,000	10,000
Accrued interest payable	417	299
Subordinated notes – fixed-to-floating rate | Carrying Amount
Liabilities
Subordinated notes	14,459	6,560
Level 1 | Estimated Fair Value
Assets
Cash and cash equivalents	118,514	78,638
Fair Value	258	254
Other assets	726	713
Level 2 | Estimated Fair Value
Assets
Fair Value	52,242	58,649
Mortgage loans held for sale	64,120	48,312
Accrued interest receivable	3,107	3,048
Liabilities
Deposits	1,180,755	1,089,261
FHLB Topeka Borrowings – fixed rate	10,060	10,003
Accrued interest payable	417	299
Level 3 | Estimated Fair Value
Assets
Loans, net	1,024,928	974,142
Level 3 | Subordinated notes – fixed-to-floating rate | Estimated Fair Value
Liabilities
Subordinated notes	$ 13,800	$ 6,004