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, 2018	May 31, 2017	May 31, 2016
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	$ 245,322	$ 240,677	$ 246,881
Permanent differences (1)	(47,137)	(29,414)	0
State and local income taxes, net of federal benefit	24,783	19,210	16,339
Other (2)	(4,451)	(355)	(6,510)
Deemed repatriation of non-U.S. earnings, net of foreign tax credits and other (collectively, transition tax)	9,768	0	0
Non-U.S. withholding taxes related to certain non-U.S. earnings subject to repatriation	4,363	0	0
Remeasurement of U.S. net deferred tax liabilities from 35% to 21%	(175,579)	0	0
Income taxes	$ 57,069	$ 230,118	$ 256,710