Accumulated Other Comprehensive Income (Loss) - Reclassification Out of Accumulated Other Comprehensive Income (Loss) (Details) - Reclassification Out of Accumulated Other Comprehensive Income (Loss) [Member] - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Nov. 30, 2017	Nov. 30, 2016	Nov. 30, 2017	Nov. 30, 2016
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Salaries and employee benefits	$ 30	$ 30	$ 60	$ 60
Provision for income taxes	(11)	(11)	(22)	(22)
Net income	$ 19	$ 19	$ 38	$ 38