LOANS, Past Due (Details) $ in Thousands	3 Months Ended		12 Months Ended
	Jun. 30, 2020 USD ($) Loan		Dec. 31, 2019 USD ($) Loan
Financing Receivable, Recorded Investment, Aging [Abstract]
Non-accrual	$ 15,383	[1]	$ 11,091	[2]
Total past due	25,351		13,306
Current	5,419,031		5,327,232
Loans	$ 5,444,382		$ 5,340,538
Number of real estate loans more than 90 days past due on contractual balloon payment | Loan	6		2
30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due	$ 5,697		$ 681
60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due	580		1
Loans 90 Days or More Past Due and Still Accruing Interest [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due	3,691		1,533
Real Estate Loans [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Non-accrual	5,199	[1]	1,007	[2]
Total past due	15,157		3,171
Current	4,796,244		4,999,183
Loans	4,811,401		5,002,354
Real Estate Loans [Member] | 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due	5,695		631
Real Estate Loans [Member] | 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due	572		0
Real Estate Loans [Member] | Loans 90 Days or More Past Due and Still Accruing Interest [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due	3,691		1,533
Real Estate Loans [Member] | One- to-Four Family Residential, Including Condominium and Cooperative Apartment [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Non-accrual	819	[1]	794	[2]
Total past due	925		1,211
Current	181,339		147,218
Loans	182,264		148,429
Real Estate Loans [Member] | One- to-Four Family Residential, Including Condominium and Cooperative Apartment [Member] | 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due	0		417
Real Estate Loans [Member] | One- to-Four Family Residential, Including Condominium and Cooperative Apartment [Member] | 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due	62		0
Real Estate Loans [Member] | One- to-Four Family Residential, Including Condominium and Cooperative Apartment [Member] | Loans 90 Days or More Past Due and Still Accruing Interest [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due	44		0
Real Estate Loans [Member] | Multifamily Residential and Residential Mixed-Use [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Non-accrual	1,377	[1]	153	[2]
Total past due	7,072		1,536
Current	2,981,439		3,383,839
Loans	2,988,511		3,385,375
Real Estate Loans [Member] | Multifamily Residential and Residential Mixed-Use [Member] | 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due	3,705		214
Real Estate Loans [Member] | Multifamily Residential and Residential Mixed-Use [Member] | 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due	510		0
Real Estate Loans [Member] | Multifamily Residential and Residential Mixed-Use [Member] | Loans 90 Days or More Past Due and Still Accruing Interest [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due	1,480		1,169
Real Estate Loans [Member] | Commercial Real Estate and Commercial Mixed-Use [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Non-accrual	3,003	[1]	60	[2]
Total past due	7,160		424
Current	1,496,860		1,349,761
Loans	1,504,020		1,350,185
Real Estate Loans [Member] | Commercial Real Estate and Commercial Mixed-Use [Member] | 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due	1,990		0
Real Estate Loans [Member] | Commercial Real Estate and Commercial Mixed-Use [Member] | 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due	0		0
Real Estate Loans [Member] | Commercial Real Estate and Commercial Mixed-Use [Member] | Loans 90 Days or More Past Due and Still Accruing Interest [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due	2,167		364
Real Estate Loans [Member] | ADC [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Non-accrual	0	[1]	0	[2]
Total past due	0		0
Current	136,606		118,365
Loans	136,606		118,365
Real Estate Loans [Member] | ADC [Member] | 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due	0		0
Real Estate Loans [Member] | ADC [Member] | 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due	0		0
Real Estate Loans [Member] | ADC [Member] | Loans 90 Days or More Past Due and Still Accruing Interest [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due	0		0
C&I [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Non-accrual	10,176	[1]	10,082	[2]
Total past due	10,176		10,126
Current	621,342		326,286
Loans	631,518		336,412
C&I [Member] | 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due	0		44
C&I [Member] | 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due	0		0
C&I [Member] | Loans 90 Days or More Past Due and Still Accruing Interest [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due	0		0
Other Loans [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Non-accrual	8	[1]	2	[2]
Total past due	18		9
Current	1,445		1,763
Loans	1,463		1,772
Other Loans [Member] | 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due	2		6
Other Loans [Member] | 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due	8		1
Other Loans [Member] | Loans 90 Days or More Past Due and Still Accruing Interest [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due	$ 0		$ 0

[1] Includes all loans on non-accrual status regardless of the number of days such loans were delinquent as of June 30, 2020.

[2] Includes all loans on non-accrual status regardless of the number of days such loans were delinquent as of December 31, 2019.