LOANS HELD FOR INVESTMENT AND ALLOWANCE FOR CREDIT LOSSES, (Narratives) (Details)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020 USD ($) Contracts	Sep. 30, 2019 USD ($) Contracts	Sep. 30, 2020 USD ($) Contracts	Sep. 30, 2019 USD ($) Contracts	Dec. 31, 2019 USD ($)	Jun. 30, 2020 USD ($)	Jan. 01, 2020 USD ($)
Financing Receivable, Allowance for Credit Loss	$ 23,137,000		$ 23,137,000		$ 13,905,000	$ 22,457,000	$ 17,174,000
Provision for credit losses	1,265,000		7,870,000
Net loan charge-offs	(585,000)		(1,907,000)
Accrued interest receivable	7,300,000		7,300,000		5,500,000
Interest income on nonaccrual loans			28,000
Real estate loans for which formal foreclosure proceedings were in process	1,200,000		1,200,000		600,000
TDRs	15,300,000		15,300,000		17,600,000
TDRs performing in accordance with modified terms			14,700,000		16,900,000
Estimated loan loss reserves	$ 800,000		$ 800,000		1,500,000
Number of Contracts | Contracts	0	4	3	7
TDRs, for which there was a payment default and the loans were modified within the twelve months prior to default	$ 0		$ 0
Loan modified with a recorded investment		$ 300,000	200,000	$ 500,000
Purchase of real estate secured adjustable rate loans			29,500,000
Net deferred fees	1,300,000		1,300,000
Loans and Leases Receivable net deferred costs					1,800,000
Payment Deferral Due to Covid-19 [Member]
Financing Receivable, Allowance for Credit Loss	$ 6,000,000.0		6,000,000.0
Provision for credit losses			7,900,000
Net loan charge-offs			$ 1,900,000
Impact of Adoption of ASC 326 [Member]
Financing Receivable, Allowance for Credit Loss					$ 3,269,000		3,300,000
Pre-tax cumulative effect transition adjustment							$ 3,300,000