Accumulated Other Comprehensive Income - Reclassification Out of Accumulated Other Comprehensive Income (Loss) (Details) - Reclassification Out of Accumulated Other Comprehensive Income (Loss) [Member] - USD ($) $ in Millions	12 Months Ended
	May 31, 2020	May 31, 2019	May 31, 2018
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Other retirement plans (expense) income	$ 107	$ 120	$ 121
Provision for income taxes	(25)	(28)	(36)
Net income	$ 82	$ 92	$ 85