Income Taxes - Components of Income Tax Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	May. 31, 2015	May. 31, 2014	May. 31, 2013
Income tax expense for continuing operations consists of the following components:
Federal	$ 201,992	$ 162,679	$ 109,739
State and local	25,230	21,268	12,453
Current income tax expense	227,222	183,947	122,192
Deferred	14,174	48,810	61,897
Income taxes	$ 241,396	$ 232,757	$ 184,089