BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES - Revenue Recognition (Details) - USD ($) $ in Thousands	2 Months Ended	3 Months Ended										8 Months Ended		12 Months Ended
	Dec. 31, 2018	Oct. 31, 2018	Jul. 31, 2018	Apr. 30, 2018	Jan. 31, 2018	Oct. 31, 2017	Jul. 31, 2017	Apr. 30, 2017	Jan. 31, 2017	Oct. 31, 2016	Jul. 31, 2016	Dec. 31, 2018	Dec. 31, 2017	Apr. 30, 2018	Apr. 30, 2017	Apr. 30, 2016	May 01, 2018
Disaggregation of Revenue [Line Items]
Performance obligation, description of timing												one year or less
Retained earnings	$ (429,048)			$ (395,669)				$ (466,541)				$ (429,048)		$ (395,669)	$ (466,541)
Real estate rentals												117,575
Revenue												4,296
Revenues	$ 30,287	$ 45,638	$ 45,946	$ 44,185	$ 42,716	$ 41,866	$ 40,978	$ 42,811	$ 39,797	$ 39,195	$ 38,301	$ 121,871	$ 111,249	$ 169,745	$ 160,104	$ 145,500
Product Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration risk, percent												100.00%
Product Concentration Risk | Rental Revenue
Disaggregation of Revenue [Line Items]
Concentration risk, percent												96.50%
Product Concentration Risk | Other Property Revenue
Disaggregation of Revenue [Line Items]
Concentration risk, percent												3.50%
Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
Disaggregation of Revenue [Line Items]
Retained earnings																	$ 627