Stock-Based Compensation - Schedule of Stock Option Vesting (Details) - USD ($) $ in Millions	12 Months Ended
May 31, 2020	May 31, 2019	May 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award Options Additional Disclosures Abstract
Vested during the year	2,073,310	2,249,301	2,465,493
Fair value	$ 99	$ 115	$ 112

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=116856206&loc=d3e5070-113901

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