SUPPLEMENTAL CASH FLOW INFORMATION - Disclosure of Non-Cash Investing and Financing Activities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Supplemental Cash Flow Elements [Abstract]
Interest paid, net of capitalized interest	$ 49,492	$ 48,160	$ 39,354
Distributions payable	23,268	23,953	23,757
Distribution fees payable to affiliates	10,188	18,492	26,071
Distributions reinvested in common stock	$ 35,163	$ 48,185	$ 45,828