DERIVATIVE INSTRUMENTS - Notional Amount (Details) - Derivative instruments not designated as hedging instruments	3 Months Ended	9 Months Ended
	Sep. 30, 2020 USD ($) Investments investment	Sep. 30, 2020 USD ($) Investments investment	Dec. 31, 2019 USD ($) investment
Interest Rate Swap
Derivative [Line Items]
Number of Instruments | investment	10	10	11
Notional Amount | $	$ 1,140,640,000	$ 1,140,640,000	$ 960,963,000
Weighted-Average Fix Pay Rate		1.90%
Weighted-Average Remaining Term in Years		2 years 1 month 6 days
Number of instruments expired | Investments	1	1
Interest Rate Swap | Minimum | One-month LIBOR
Derivative [Line Items]
Reference Rate	1.16%	1.16%
Interest Rate Swap | Maximum | One-month LIBOR
Derivative [Line Items]
Reference Rate	2.11%	2.11%
Interest Rate Swap Which Will Become Effective in 2020 and Mature in 2023
Derivative [Line Items]
Number of Instruments | investment	1	1
Notional Amount | $	$ 65,000,000.0	$ 65,000,000.0