FAIR VALUE - Summary of assets measured at fair value on recurring basis (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Summary of assets measured on a recurring and nonrecurring basis
Available-for-sale securities, at fair value	$ 40,654	$ 58,903
U.S. Treasury debt
Summary of assets measured on a recurring and nonrecurring basis
Available-for-sale securities, at fair value	256	254
Corporate bonds
Summary of assets measured on a recurring and nonrecurring basis
Available-for-sale securities, at fair value	2,048
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
Guarantee liability	153
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 bonds
Summary of assets measured on a recurring and nonrecurring basis
Available-for-sale securities, at fair value	2,048
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 bonds
Summary of assets measured on a recurring and nonrecurring basis
Available-for-sale securities, at fair value	2,048
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 | Recurring
Summary of assets measured on a recurring and nonrecurring basis
Guarantee asset	245
Guarantee liability	153
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