SCHEDULE III REAL ESTATE AND ACCUMULATED DEPRECIATION - Summary (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Carrying cost
Balance at beginning of period	$ 1,198,686	$ 949,838	$ 937,617
Acquisitions	74,923	206,340	11,650
Improvements	49,134	33,463	48,102
Conversion of mortgage loans into owned properties		10,600
Capitalized interest	1,408	827	1,506
Other non-cash items (See Note 4)	2,460	2,882	304
Conveyed land (See Note 4)		(670)
Cost of real estate sold	(24,282)	(2,344)	(49,341)
Impairment on real estate for sale	(766)	(2,250)
Ending balance	1,301,563	1,198,686	949,838
Accumulated depreciation
Balance at beginning of period	251,265	223,315	218,700
Depreciation expense	35,809	29,329	25,424
Cost of real estate sold	(11,213)	(1,379)	(20,809)
Ending balance	$ 275,861	$ 251,265	$ 223,315