BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES - Identified Intangible Assets and Liabilities (Details) - USD ($)	3 Months Ended
	Jul. 31, 2017	Jul. 31, 2016	Apr. 30, 2017
Identified Intangible Assets and Liabilities and Goodwill [Abstract]
Finite-lived Intangible Assets Acquired	$ 870,000	$ 0
Addition to intangible liabilities	$ 89,000	$ 0
Weighted average lives of intangible assets acquired	10 months 24 days	0 years
Identified intangible assets (included in intangible assets) [Abstract]
Gross carrying amount	$ 6,973,000		$ 6,102,000
Accumulated amortization	(5,724,000)		(5,444,000)
Net carrying amount	1,249,000		658,000
Identified intangible liabilities (included in other liabilities) [Abstract]
Gross carrying amount	246,000		156,000
Accumulated amortization	(84,000)		(76,000)
Net carrying amount	$ 162,000		$ 80,000