Stock-Based Compensation - Schedule of Stock Option Vesting (Details) - USD ($) $ in Millions	12 Months Ended
May 31, 2019	May 31, 2018	May 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award Options Additional Disclosures Abstract
Vested during the year	2,249,301	2,465,493	2,427,837
Fair value	$ 115	$ 112	$ 104

Fair value of options vested. Excludes equity instruments other than options, for example, but not limited to, share units, stock appreciation rights, restricted stock.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

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