DEBT - Schedule of Debt (Details) - USD ($) $ in Thousands	8 Months Ended
	Dec. 31, 2018	Apr. 30, 2018	Apr. 30, 2017
Debt Instrument [Line Items]
Carrying principal value	$ 648,474	$ 706,140	$ 786,030
Fixed Rate Mortgages Payable
Debt Instrument [Line Items]
Carrying principal value	$ 445,974	489,401	629,535
Weighted average maturity in years	3 years 7 months 10 days
Variable Rate Mortgages Payable
Debt Instrument [Line Items]
Carrying principal value	$ 0	$ 22,739	$ 57,708
Mortgages
Debt Instrument [Line Items]
Weighted average interest rate	4.58%	4.69%	4.71%
Construction Loans
Debt Instrument [Line Items]
Carrying principal value	$ 0	$ 0	$ 41,737
Weighted average interest rate	0.00%	0.00%	3.27%
Unsecured Debt
Debt Instrument [Line Items]
Carrying principal value	$ 202,500	$ 194,000	$ 57,050
Unsecured Debt | Line of Credit
Debt Instrument [Line Items]
Carrying principal value	$ 57,500	$ 124,000	$ 57,050
Weighted average maturity in years	3 years 8 months 1 day
Weighted average interest rate	3.72%	3.35%	2.67%
Unsecured Debt | Medium-term Notes
Debt Instrument [Line Items]
Carrying principal value	$ 145,000	$ 70,000	$ 0
Weighted average maturity in years	5 years 10 months 10 days
Weighted average interest rate	4.01%	3.86%	0.00%