VARIABLE INTEREST ENTITIES - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Variable Interest Entity [Line Items]
Total assets	$ 7,738,106	$ 7,828,410		$ 7,738,106
Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Funding transferred	0		$ 0	3,631	$ 235
Total assets	253,380	259,445		253,380
Maximum loss exposure	27,786	32,525		27,786
Variable Interest Entity, Not Primary Beneficiary | Other Assets
Variable Interest Entity [Line Items]
Total assets	$ 27,800	29,300		$ 27,800
Variable Interest Entity, Not Primary Beneficiary | Multifamily
Variable Interest Entity [Line Items]
Funding transferred		$ 573,500
Credit losses guaranteed (percent)	12.00%			12.00%
Repurchase liability recognized	$ 3,500			$ 3,500
Maximum loss exposure	$ 68,800			$ 68,800