Income Taxes - Reconciliation of Income Tax Expense Using the Statutory Rate and Actual Income Tax Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	May 31, 2016	May 31, 2015	May 31, 2014
Reconciliation of income tax expense for continuing operations using the statutory rate and actual income tax expense is as follows:
Income taxes at the U.S. federal statutory rate	$ 251,352	$ 228,727	$ 187,375
State and local income taxes, net of federal benefit	16,672	16,705	17,934
Other	(6,843)	(2,629)	(5,954)
Income taxes	$ 261,181	$ 242,803	$ 199,355