RELATED-PARTY TRANSACTIONS AND ARRANGEMENTS (Advisory Fees and Expenses) (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Advisors | Advisory fees
Related Party Transaction [Line Items]
Reimbursement of expense threshold, percent of average assets		2.00%		2.00%
Reimbursement of expense threshold, percent of net income		25.00%		25.00%
Expenses exceeding the average asset value percent threshold		$ 864,000		$ 864,000
Expenses waived	$ 91,000		$ 269,000
Expenses exceeding the average asset value percent threshold	$ 1,300,000		$ 1,300,000
Average invested assets between $0 to $2 billion | Advisors | Advisory fees
Related Party Transaction [Line Items]
Annualized rate percentage paid on average invested asset	0.75%		0.75%
Average invested assets between $2 billion to $4 billion | Advisors | Advisory fees
Related Party Transaction [Line Items]
Annualized rate percentage paid on average invested asset	0.70%		0.70%
Average invested assets over $4 bilion | Advisors | Advisory fees
Related Party Transaction [Line Items]
Annualized rate percentage paid on average invested asset	0.65%		0.65%
Minimum | Average invested assets between $0 to $2 billion
Related Party Transaction [Line Items]
Average invested assets	$ 0		$ 0
Minimum | Average invested assets between $2 billion to $4 billion
Related Party Transaction [Line Items]
Average invested assets	2,000,000,000.0		2,000,000,000.0
Minimum | Average invested assets over $4 bilion
Related Party Transaction [Line Items]
Average invested assets	4,000,000,000.0		4,000,000,000.0
Maximum | Average invested assets between $0 to $2 billion
Related Party Transaction [Line Items]
Average invested assets	2,000,000,000.0		2,000,000,000.0
Maximum | Average invested assets between $2 billion to $4 billion
Related Party Transaction [Line Items]
Average invested assets	$ 4,000,000,000.0		$ 4,000,000,000.0