Income Taxes - Components of Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	May 31, 2017	May 31, 2016	May 31, 2015
Income tax expense for continuing operations consists of the following components:
Federal	$ 194,130	$ 279,134	$ 199,360
State and local	27,197	25,428	24,733
Current income tax expense	221,327	304,562	224,093
Deferred	8,791	(47,852)	13,910
Income taxes	$ 230,118	$ 256,710	$ 238,003