TRANSACTIONS WITH RELATED PARTIES (Details)	12 Months Ended
	Apr. 30, 2016 USD ($) loan	Apr. 30, 2015 USD ($)	Apr. 30, 2014 USD ($)	Apr. 30, 2013 USD ($) ft²
BANKING SERVICES [Abstract]
Maximum borrowing capacity	$ 100,000,000
Compensating balance	13,160,000
Interest and fees paid amount		$ 1,700,000	$ 1,000,000
LEASE TRANSACTION [Abstract]
Sale price	$ 536,728,000	$ 88,867,000
Mortgages Payable [Member]
BANKING SERVICES [Abstract]
Variable interest rate (in hundredths)	4.54%	5.16%
Multi bank Line of Credit [Member]
BANKING SERVICES [Abstract]
Maximum borrowing capacity	$ 100,000,000
First International Bank & Trust [Member]
BANKING SERVICES [Abstract]
Bank service and other fees charged	500	$ 500	500
Interest and fees paid amount	$ 2,500,000	2,000,000	1,200,000
LEASE TRANSACTION [Abstract]
Area of building constructed (in square feet) | ft²				3,700
Lease term	20 years
Total cost to construct building				$ 1,300,000
Net rental payments received per year	$ 108,000	109,000	109,000
Sale price	1,700,000
First International Bank & Trust [Member] | Multi bank Line of Credit [Member]
BANKING SERVICES [Abstract]
Maximum borrowing capacity	11,000,000
Interest paid	186,000	245,000	125,000
Bank services charges and fee	77,000	$ 40,000	$ 40,000
Compensating balance	6,000,000
Non interest bearing account	1,500,000
Interest bearing account	$ 4,500,000
Percentage interest on deposited amount (in hundredths)	0.20%
Renaissance Heights I - Williston ND [Member] | First International Bank & Trust [Member] | Mortgages Payable [Member]
BANKING SERVICES [Abstract]
Number of mortgage loans outstanding | loan	1
Original principal balance	$ 43,000,000
Variable interest rate (in hundredths)	5.24%
Interest paid	$ 2,200,000
Carrying principal balance	42,200,000
Robert W Baird and Co Incorporated [Member]
Sales Agreement [Abstract]
Aggregate offering price	$ 75,000,000
Compensation of gross sales price (in hundredths)	2.00%