SCHEDULE III REAL ESTATE AND ACCUMULATED DEPRECIATION - Summary (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Carrying cost
Balance at beginning of period	$ 1,484,571	$ 1,421,456	$ 1,392,122
Acquisitions	13,581	58,414	40,408
Improvements	23,612	23,363	38,528
Capitalized interest	354	608	1,248
Cost of real estate sold	(66,140)	(19,270)	(50,850)
Impairment loss from real estate investments	(3,977)
Ending balance	1,452,001	1,484,571	1,421,456
Accumulated depreciation
Balance at beginning of period	347,755	314,875	306,033
Depreciation expense	38,945	39,094	37,416
Cost of real estate sold	(37,057)	(6,214)	(28,574)
Ending balance	$ 349,643	$ 347,755	$ 314,875