SEGMENT INFORMATION - Reconciliation of Consolidated Net Income (Loss) to Consolidated NOI (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting [Abstract]
Net income	$ 16,874	$ 6,820	$ 6,252	$ 4,583	$ 121,673	$ (43,522)	$ 12,876	$ 44,445	$ 34,529	$ 135,472	$ 121,177
Plus:
Interest expense									81,512	78,199	81,886
Interest expense - amortization of deferred financing costs									2,768	2,498	2,435
Depreciation and amortization									210,005	176,000	180,323
General and administrative expenses									32,156	27,802	28,538
Equity in loss of Real Estate Ventures									9,922	15,231	8,306
Provision for impairment									0	71,707	3,057
Loss on early extinguishment of debt									0	105	3,933
Less:
Interest income									2,318	4,703	1,113
Income tax (provision) benefit									(12)	(423)	628
Net gain on disposition of real estate									356	2,932	32,017
Net gain on sale of undepreciated real estate									2,020	3,040	953
Net gain on real estate venture transactions									11,639	142,233	80,526
Gain on promoted interest in unconsolidated real estate venture									0	28,283	0
Consolidated net operating income									$ 354,571	$ 326,246	$ 314,418