FAIR VALUE - Summary of assets measured at level 3 fair value on recurring basis (Details) - USD ($) $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Summary of assets measured on a recurring and nonrecurring basis
Available-for-sale securities, at fair value	$ 40,654		$ 58,903
Other real estate owned valuation allowance			1,800
Impaired Financing Receivable, with Related Allowance, Recorded Investment	3,421		4,412
Loans and Leases Receivable, Allowance	11,845		7,875
Bank charged off			200
Other real estate owned, gross			2,400
Provision for loan losses	4,000	$ 200
Other real estate owned	558		658
Net recorded investment	8,458		11,437
U.S. Treasury debt
Summary of assets measured on a recurring and nonrecurring basis
Available-for-sale securities, at fair value	256		254
Recurring
Summary of assets measured on a recurring and nonrecurring basis
Available-for-sale securities, at fair value	40,654		58,903
Equity securities	732		713
Guarantee asset	245
Recurring | U.S. Treasury debt
Summary of assets measured on a recurring and nonrecurring basis
Available-for-sale securities, at fair value	256		254
Recurring | Corporate collateralized mortgage obligations and mortgage-backed securities
Summary of assets measured on a recurring and nonrecurring basis
Available-for-sale securities, at fair value	5,846		10,420
Recurring | Interest rate lock and forward delivery commitments
Summary of assets measured on a recurring and nonrecurring basis
Derivative asset, Fair value	11,622		1,184
Recurring | GNMA
Summary of assets measured on a recurring and nonrecurring basis
Available-for-sale securities, at fair value	29,788		45,312
Recurring | FNMA
Summary of assets measured on a recurring and nonrecurring basis
Available-for-sale securities, at fair value	2,716		2,917
Level 1 | Recurring
Summary of assets measured on a recurring and nonrecurring basis
Available-for-sale securities, at fair value	256		254
Equity securities	732		713
Level 1 | Recurring | U.S. Treasury debt
Summary of assets measured on a recurring and nonrecurring basis
Available-for-sale securities, at fair value	256		254
Level 2 | Recurring
Summary of assets measured on a recurring and nonrecurring basis
Available-for-sale securities, at fair value	40,398		58,649
Level 2 | Recurring | Corporate collateralized mortgage obligations and mortgage-backed securities
Summary of assets measured on a recurring and nonrecurring basis
Available-for-sale securities, at fair value	5,846		10,420
Level 2 | Recurring | GNMA
Summary of assets measured on a recurring and nonrecurring basis
Available-for-sale securities, at fair value	29,788		45,312
Level 2 | Recurring | FNMA
Summary of assets measured on a recurring and nonrecurring basis
Available-for-sale securities, at fair value	2,716		2,917
Level 3
Summary of assets measured on a recurring and nonrecurring basis
Impaired Financing Receivable, with Related Allowance, Recorded Investment	3,400		4,400
Loans and Leases Receivable, Allowance	1,400		800
Provision for loan losses	1,400		800
Level 3 | Recurring
Summary of assets measured on a recurring and nonrecurring basis
Guarantee asset	245
Level 3 | Recurring | Interest rate lock and forward delivery commitments
Summary of assets measured on a recurring and nonrecurring basis
Derivative asset, Fair value	11,622		1,184
Commercial properties | Nonrecurring
Summary of assets measured on a recurring and nonrecurring basis
Other real estate owned	558		658
Commercial properties | Level 3 | Nonrecurring
Summary of assets measured on a recurring and nonrecurring basis
Other real estate owned	558		658
Commercial and Industrial | Nonrecurring
Summary of assets measured on a recurring and nonrecurring basis
Net recorded investment	1,998		3,579
Commercial and Industrial | Level 3 | Nonrecurring
Summary of assets measured on a recurring and nonrecurring basis
Net recorded investment	$ 1,998		$ 3,579