Stock-Based Compensation - Schedule of Stock Option Vesting (Details) - USD ($) $ in Millions	12 Months Ended
May 31, 2017	May 31, 2016	May 31, 2015
Share Based Compensation Arrangement By Share Based Payment Award Options Additional Disclosures Abstract
Vested during the year	2,427,837	2,572,129	2,611,524
Fair value	$ 104	$ 98	$ 83

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://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration