LOANS, Credit Quality Indicators (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Credit Risk Profile of Real Estate Loans [Abstract]
Loans	$ 5,444,382	$ 5,340,538
Real Estate Loans [Member]
Credit Risk Profile of Real Estate Loans [Abstract]
Loans	4,811,401	5,002,354
Real Estate Loans [Member] | Pass [Member]
Credit Risk Profile of Real Estate Loans [Abstract]
Loans	4,711,077	4,919,744
Real Estate Loans [Member] | Special Mention [Member]
Credit Risk Profile of Real Estate Loans [Abstract]
Loans	52,096	19,446
Real Estate Loans [Member] | Substandard [Member]
Credit Risk Profile of Real Estate Loans [Abstract]
Loans	48,228	63,164
Real Estate Loans [Member] | Doubtful [Member]
Credit Risk Profile of Real Estate Loans [Abstract]
Loans	0	0
Real Estate Loans [Member] | One- to-Four Family Residential, Including Condominium and Cooperative Apartment [Member]
Credit Risk Profile of Real Estate Loans [Abstract]
Loans	182,264	148,429
Real Estate Loans [Member] | One- to-Four Family Residential, Including Condominium and Cooperative Apartment [Member] | Pass [Member]
Credit Risk Profile of Real Estate Loans [Abstract]
Loans	181,368	147,635
Real Estate Loans [Member] | One- to-Four Family Residential, Including Condominium and Cooperative Apartment [Member] | Special Mention [Member]
Credit Risk Profile of Real Estate Loans [Abstract]
Loans	0	0
Real Estate Loans [Member] | One- to-Four Family Residential, Including Condominium and Cooperative Apartment [Member] | Substandard [Member]
Credit Risk Profile of Real Estate Loans [Abstract]
Loans	896	794
Real Estate Loans [Member] | One- to-Four Family Residential, Including Condominium and Cooperative Apartment [Member] | Doubtful [Member]
Credit Risk Profile of Real Estate Loans [Abstract]
Loans	0	0
Real Estate Loans [Member] | Multifamily Residential and Residential Mixed-Use [Member]
Credit Risk Profile of Real Estate Loans [Abstract]
Loans	2,988,511	3,385,375
Real Estate Loans [Member] | Multifamily Residential and Residential Mixed-Use [Member] | Pass [Member]
Credit Risk Profile of Real Estate Loans [Abstract]
Loans	2,907,528	3,319,226
Real Estate Loans [Member] | Multifamily Residential and Residential Mixed-Use [Member] | Special Mention [Member]
Credit Risk Profile of Real Estate Loans [Abstract]
Loans	47,313	14,606
Real Estate Loans [Member] | Multifamily Residential and Residential Mixed-Use [Member] | Substandard [Member]
Credit Risk Profile of Real Estate Loans [Abstract]
Loans	33,670	51,543
Real Estate Loans [Member] | Multifamily Residential and Residential Mixed-Use [Member] | Doubtful [Member]
Credit Risk Profile of Real Estate Loans [Abstract]
Loans	0	0
Real Estate Loans [Member] | Commercial Real Estate and Commercial Mixed-Use [Member]
Credit Risk Profile of Real Estate Loans [Abstract]
Loans	1,504,020	1,350,185
Real Estate Loans [Member] | Commercial Real Estate and Commercial Mixed-Use [Member] | Pass [Member]
Credit Risk Profile of Real Estate Loans [Abstract]
Loans	1,485,575	1,334,518
Real Estate Loans [Member] | Commercial Real Estate and Commercial Mixed-Use [Member] | Special Mention [Member]
Credit Risk Profile of Real Estate Loans [Abstract]
Loans	4,783	4,840
Real Estate Loans [Member] | Commercial Real Estate and Commercial Mixed-Use [Member] | Substandard [Member]
Credit Risk Profile of Real Estate Loans [Abstract]
Loans	13,662	10,827
Real Estate Loans [Member] | Commercial Real Estate and Commercial Mixed-Use [Member] | Doubtful [Member]
Credit Risk Profile of Real Estate Loans [Abstract]
Loans	0	0
Real Estate Loans [Member] | ADC [Member]
Credit Risk Profile of Real Estate Loans [Abstract]
Loans	136,606	118,365
Real Estate Loans [Member] | ADC [Member] | Pass [Member]
Credit Risk Profile of Real Estate Loans [Abstract]
Loans	136,606	118,365
Real Estate Loans [Member] | ADC [Member] | Special Mention [Member]
Credit Risk Profile of Real Estate Loans [Abstract]
Loans	0	0
Real Estate Loans [Member] | ADC [Member] | Substandard [Member]
Credit Risk Profile of Real Estate Loans [Abstract]
Loans	0	0
Real Estate Loans [Member] | ADC [Member] | Doubtful [Member]
Credit Risk Profile of Real Estate Loans [Abstract]
Loans	0	0
C & I Loans [Member]
Credit Risk Profile of Real Estate Loans [Abstract]
Loans	631,518	336,412
C & I Loans [Member] | Pass [Member]
Credit Risk Profile of Real Estate Loans [Abstract]
Loans	618,214	325,296
C & I Loans [Member] | Special Mention [Member]
Credit Risk Profile of Real Estate Loans [Abstract]
Loans	2,058	1,034
C & I Loans [Member] | Substandard [Member]
Credit Risk Profile of Real Estate Loans [Abstract]
Loans	1,164	0
C & I Loans [Member] | Doubtful [Member]
Credit Risk Profile of Real Estate Loans [Abstract]
Loans	10,082	10,082
Real Estate Loans and C & I Loans [Member]
Credit Risk Profile of Real Estate Loans [Abstract]
Loans	5,442,919	5,338,766
Real Estate Loans and C & I Loans [Member] | Pass [Member]
Credit Risk Profile of Real Estate Loans [Abstract]
Loans	5,329,291	5,245,040
Real Estate Loans and C & I Loans [Member] | Special Mention [Member]
Credit Risk Profile of Real Estate Loans [Abstract]
Loans	54,154	20,480
Real Estate Loans and C & I Loans [Member] | Substandard [Member]
Credit Risk Profile of Real Estate Loans [Abstract]
Loans	49,392	63,164
Real Estate Loans and C & I Loans [Member] | Doubtful [Member]
Credit Risk Profile of Real Estate Loans [Abstract]
Loans	10,082	10,082
Other Loans [Member]
Credit Risk Profile of Real Estate Loans [Abstract]
Loans	1,463	1,772
Other Loans [Member] | Performing [Member]
Credit Risk Profile of Real Estate Loans [Abstract]
Loans	1,455	1,770
Other Loans [Member] | Non-Accrual [Member]
Credit Risk Profile of Real Estate Loans [Abstract]
Loans	$ 8	$ 2