ALLOWANCE FOR LOAN LOSSES, Impaired Real Estate Loans (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Unpaid Principal Balance [Abstract]
With related allowance recorded		$ 15,000		$ 15,000		$ 309
Total		15,225		15,225		5,999
Recorded Investment [Abstract]
With related allowance recorded	[1]	15,000		15,000		309
Total	[1]	15,225		15,225		5,999
Related Allowance [Abstract]
Related allowance		7,500		7,500		230
Average Recorded Investment [Abstract]
Total	[1]	10,614	$ 6,461	9,067	$ 7,613
Interest Income Recognized [Abstract]
Total		218	101	435	326
Real Estate Loans [Member]
Unpaid Principal Balance [Abstract]
With no related allowance recorded		225		225		5,690
Recorded Investment [Abstract]
With no related allowance recorded	[1]	225		225		5,690
Related Allowance [Abstract]
Related allowance		0		0		0
Average Recorded Investment [Abstract]
With no related allowance recorded	[1]	3,114	6,461	5,182	7,318
Interest Income Recognized [Abstract]
With no related allowance recorded		65	101	277	326
Real Estate Loans [Member] | One-to-Four Family Residential, Including Condominium and Cooperative Apartment [Member]
Unpaid Principal Balance [Abstract]
With no related allowance recorded		9		9		14
Recorded Investment [Abstract]
With no related allowance recorded	[1]	9		9		14
Related Allowance [Abstract]
Related allowance		0		0		0
Average Recorded Investment [Abstract]
With no related allowance recorded	[1]	10	17	11	19
Interest Income Recognized [Abstract]
With no related allowance recorded		4	0	4	0
Real Estate Loans [Member] | Multifamily Residential and Residential Mixed-Use [Member]
Unpaid Principal Balance [Abstract]
With no related allowance recorded		153		153		551
Recorded Investment [Abstract]
With no related allowance recorded	[1]	153		153		551
Related Allowance [Abstract]
Related allowance		0		0		0
Average Recorded Investment [Abstract]
With no related allowance recorded	[1]	416	1,174	480	892
Interest Income Recognized [Abstract]
With no related allowance recorded		7	8	29	43
Real Estate Loans [Member] | Commercial Real Estate and Commercial Mixed-Use [Member]
Unpaid Principal Balance [Abstract]
With no related allowance recorded		63		63		5,125
Recorded Investment [Abstract]
With no related allowance recorded	[1]	63		63		5,125
Related Allowance [Abstract]
Related allowance		0		0		0
Average Recorded Investment [Abstract]
With no related allowance recorded	[1]	2,688	5,270	4,691	6,407
Interest Income Recognized [Abstract]
With no related allowance recorded		54	93	244	283
C&I [Member]
Unpaid Principal Balance [Abstract]
With related allowance recorded		15,000		15,000		309
Recorded Investment [Abstract]
With related allowance recorded	[1]	15,000		15,000		309
Related Allowance [Abstract]
Related allowance		7,500		7,500		$ 230
Average Recorded Investment [Abstract]
With an allowance recorded	[1]	7,500	0	3,885	295
Interest Income Recognized [Abstract]
With an allowance recorded		$ 153	$ 0	$ 159	$ 0

[1] The recorded investment excludes accrued interest receivable and deferred costs due to immateriality.