DEBT - Narrative (Details)	9 Months Ended
	Jan. 31, 2018 USD ($) property	Apr. 30, 2017 USD ($)
Line of Credit Facility [Line Items]
Number of real estate properties, unencumbered by mortgages | property	34
Number of real estate properties, unencumbered used to provide credit support | property	25
Number of real estate properties | property	99
Revolving line of credit	$ 67,000,000	$ 57,050,000
Carrying principal balance	692,874,000	786,030,000
Line of Credit [Member] | BMO Line of Credit [Member]
Line of Credit Facility [Line Items]
Maximum borrowing capacity	300,000,000
Current borrowing capacity	219,200,000
Remaining borrowing capacity	152,100,000
Revolving line of credit	$ 67,000,000
Minimum [Member] | London Interbank Offered Rate (LIBOR) [Member] | Line of Credit [Member]
Line of Credit Facility [Line Items]
Basis spread on variable rate	1.60%
Maximum [Member] | London Interbank Offered Rate (LIBOR) [Member] | Line of Credit [Member]
Line of Credit Facility [Line Items]
Basis spread on variable rate	2.25%
Unsecured Debt [Member]
Line of Credit Facility [Line Items]
Debt instrument face amount	$ 70,000,000.0
Line of Credit [Member]
Line of Credit Facility [Line Items]
Maximum borrowing capacity	370,000,000
Line of credit facility, accordion feature, higher borrowing capacity option	$ 500,000,000
Construction Loan Payable [Member]
Line of Credit Facility [Line Items]
Carrying principal balance		$ 41,700,000
Weighted average interest rate		3.27%