Summary of Significant Accounting Policies (Details) - USD ($) $ in Millions	3 Months Ended
	Aug. 31, 2017	Aug. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Excess tax benefit, amount	$ 88
Cash provided by operations	575	$ 788
Cash used by financing activities	$ 998	1,202
Accounting Standard Update 2016-09, Excess Tax Benefit Component
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cash provided by operations		59
Cash used by financing activities		59
Accounting Standard Update 2016-09, Statutory Tax Withholding Component
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cash provided by operations		8
Cash used by financing activities		$ 8