Note 6 - Long-term Debt and Capital Leases - Long-term Debt and Capital Lease Obligations (Details) - USD ($)	Feb. 28, 2017	May 31, 2016	May 14, 2012
Unamortized debt issuance costs	$ (31,000)	$ (74,000)
Mortgage loan obligations	5,135,000	15,745,000
Unamortized (discount)/premium - mortgage loan obligations	(2,000)	75,000
Capital lease obligations	207,000	211,000
Total long-term debt and capital leases	213,882,000	223,737,000
Less current maturities	349,000	9,934,000
Long-term debt and capital leases, less current maturities	213,533,000	213,803,000
Senior Notes [Member]
Senior unsecured notes	212,546,000	212,546,000
Unamortized discount	(1,476,000)	(1,771,000)	$ (3,700,000)
Unamortized debt issuance costs	(2,497,000)	(2,995,000)
Senior unsecured notes less unamortized discount and debt issuance costs	$ 208,573,000	$ 207,780,000