Reconciliation Between Statutory Federal Income Tax Rate and Effective Income Tax Rate from Continuing Operations (Detail)	12 Months Ended
	May. 31, 2015	May. 31, 2014	May. 31, 2013
Schedule of Effective Tax Rate Reconciliation [Line Items]
Statutory federal rate	35.00%	35.00%	35.00%
State taxes, net of federal benefit	2.90%	2.50%	3.00%
Foreign tax refund	(0.80%)	(0.60%)	0.00%
Permanent differences resulting from valuation allowances	0.60%	0.30%	0.70%
Other	(0.30%)	0.10%	0.00%
Effective tax rate	37.40%	37.30%	38.70%