LOANS - Commercial Real Estate Amortized Cost Basis by Risk Rating and Vintage (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) loan	Sep. 30, 2019 USD ($)
Financing Receivable, Credit Quality Indicator [Line Items]
Loan loss provision	$ (21,993)	$ 3,504	$ 146,084	$ 9,207
Commercial Mortgage
Financing Receivable, Credit Quality Indicator [Line Items]
Total	1,456,459		1,456,459
2020	158,076		158,076
2019	543,701		543,701
2018	377,826		377,826
2017	176,674		176,674
2016	68,358		68,358
Prior	131,824		131,824
Accrued interest receivable	4,100		4,100
Performing | Commercial Mortgage
Financing Receivable, Credit Quality Indicator [Line Items]
Total	354,960		354,960
2020	92,076		92,076
2019	168,409		168,409
2018	0		0
2017	12,447		12,447
2016	0		0
Prior	82,028		82,028
Closely Monitored | Commercial Mortgage
Financing Receivable, Credit Quality Indicator [Line Items]
Total	158,701		158,701
2020	0		0
2019	158,701		158,701
2018	0		0
2017	0		0
2016	0		0
Prior	0		0
Special Mention | Commercial Mortgage
Financing Receivable, Credit Quality Indicator [Line Items]
Total	676,700		676,700
2020	56,845		56,845
2019	216,591		216,591
2018	270,767		270,767
2017	64,139		64,139
2016	68,358		68,358
Prior	0		0
Substandard | Commercial Mortgage
Financing Receivable, Credit Quality Indicator [Line Items]
Total	169,058		169,058
2020	9,155		9,155
2019	0		0
2018	67,391		67,391
2017	42,716		42,716
2016	0		0
Prior	49,796		49,796
Doubtful | Commercial Mortgage
Financing Receivable, Credit Quality Indicator [Line Items]
Total	97,040		97,040
2020	0		0
2019	0		0
2018	39,668		39,668
2017	57,372		57,372
2016	0		0
Prior	0		0
Loss | Commercial Mortgage
Financing Receivable, Credit Quality Indicator [Line Items]
Total	0		0
2020	0		0
2019	0		0
2018	0		0
2017	0		0
2016	0		0
Prior	$ 0		$ 0
Mezzanine loans | Commercial Mortgage
Financing Receivable, Credit Quality Indicator [Line Items]
Number of loans | loan			2
Loan loss provision			$ 46,600