Income Taxes - Reconciliation of Income Tax Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	May 31, 2020	May 31, 2019	May 31, 2018
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	$ 222,258	$ 231,503	$ 245,322
Permanent differences	(67,075)	(51,201)	(47,137)
State and local income taxes, net of federal benefit	25,294	31,687	24,783
Other	1,454	6,506	(4,451)
Impact of the Tax Cuts and Jobs Act:
Deemed repatriation of non-U.S. earnings, net of foreign tax credits and other (collectively, transition tax)	0	153	9,768
Non-U.S. withholding taxes related to certain non-U.S. earnings subject to repatriation	0	690	4,363
Remeasurement of U.S. net deferred tax liabilities from 35% to 21%	0	426	(175,579)
Income taxes	$ 181,931	$ 219,764	$ 57,069