SIGNIFICANT ACCOUNTING POLICIES (Details) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
	Jun. 29, 2017	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Percentage of commercial mortgage backed securities with below AA rating		4.10%								4.10%
Reduction in depreciation and amortization										$ (40,332)	$ (39,447)	$ (39,061)
Additional state taxes		$ 3,057	$ (576)	$ 6,606	$ (1,375)	$ 773	$ 8,721	$ (2,301)	$ (873)	7,712	6,320	14,557
Additional return on equity from Company's investments										0	1,017	294
Mortgage loans on real estate, transfered to securitization	$ 625,700
Net cash provided by (used in) operating activities										11,985	338,427	(38,307)
Net cash provided by (used in) investing activities										(306,635)	36,284	34,650
Accounting Standards Update 2016-15
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net cash provided by (used in) operating activities										(52,000)	(70,100)	(79,100)
Net cash provided by (used in) investing activities										$ 52,000	$ 70,100	$ 79,100
Out-of-Period Adjustment Related to Prior Years
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Reduction in depreciation and amortization		600			$ 800
Additional deferred financing cost amortization									500
Out-of-Period Adjustment Related to Prior Years | Noncontrolling Interests in Consolidated Joint Ventures
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Additional return on equity from Company's investments									900
Out-of-Period Adjustment Related to Prior Years | Tax Year 2015 | State and Local Jurisdiction
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Additional state taxes									$ 1,200
Out-of-Period Adjustment
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Reduction in depreciation and amortization		$ 1,200
Building | Minimum
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Estimated useful lives of real estate										20 years
Building | Maximum
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Estimated useful lives of real estate										47 years
Building Fixtures and Improvements | Minimum
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Estimated useful lives of real estate										4 years
Building Fixtures and Improvements | Maximum
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Estimated useful lives of real estate										15 years