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, 2017	May 31, 2016	May 31, 2015
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	$ 240,677	$ 246,881	$ 224,360
State and local income taxes, net of federal benefit	19,210	16,339	16,308
Other	(29,769)	(6,510)	(2,665)
Income taxes	230,118	$ 256,710	$ 238,003
Accounting Standards Update 2016-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
The total income tax benefit recognized in the consolidated income statement for share-based compensation arrangements	$ 29,400