Note 9 - Long-term Debt - Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Nov. 30, 2016	Nov. 30, 2015	Nov. 30, 2016	Nov. 30, 2015
Amortization of deferred financing costs	$ 1,774	$ 1,781	$ 3,514	$ 3,533
Interest rate swaps and other interest	48	153	176	369
Revolving facility fees and interest	342	249	549	409
Interest accreted on contingent consideration liabilities	1,012	286	1,994	567
Total interest expense	23,127	22,454	46,229	44,946
Term Loan Facility [Member]
Interest Expense Including OID Amortization	8,648	8,702	17,396	17,506
Notes Payable, Other Payables [Member]
Interest Expense Including OID Amortization	$ 11,303	$ 11,283	$ 22,600	$ 22,562