DERIVATIVE INSTRUMENTS DERIVATIVE INSTRUMENTS - Schedule of Derivatives (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Oct. 31, 2018	Oct. 31, 2017	Oct. 31, 2018	Oct. 31, 2017	Apr. 30, 2018
Derivative [Line Items]
Interest expense	$ 7,997	$ 8,509	$ 16,382	$ 16,640
Net income (loss)	(5,611)	13,139	(1,895)	(140)
Accumulated Gain (Loss), Cash Flow Hedge, Including Noncontrolling Interest [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Derivative [Line Items]
Net income (loss)	90	0	119	0
Accumulated Gain (Loss), Cash Flow Hedge, Including Noncontrolling Interest [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Interest expense	90	0	119	0
Designated as Hedging Instrument [Member]
Derivative [Line Items]
Fair value	3,321		3,321		$ 1,779
Gain (Loss) Recognized in OCI	1,247	0	1,455	0
Designated as Hedging Instrument [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Gain (Loss) Recognized in OCI	1,247	$ 0	1,455	$ 0
Designated as Hedging Instrument [Member] | Other Assets [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Fair value	$ 3,321		$ 3,321		$ 1,779