Income Taxes - Reconciliation of Income Tax Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	May 31, 2021	May 31, 2020	May 31, 2019
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	$ 270,427	$ 222,258	$ 231,503
Permanent differences	(101,870)	(67,075)	(51,201)
State and local income taxes, net of federal benefit	27,304	25,294	31,687
Capital loss carryback	(14,072)	0	0
Other	(5,008)	1,454	6,506
Impact of the Tax Cuts and Jobs Act (the Tax Act):
Deemed repatriation of non-U.S. earnings, net of foreign tax credits and other (collectively, transition tax)	0	0	153
Non-U.S. withholding taxes related to certain non-U.S. earnings subject to repatriation	0	0	690
Remeasurement of U.S. net deferred tax liabilities from 35% to 21%	0	0	426
Income taxes	$ 176,781	$ 181,931	$ 219,764