Retirement Plans - Schedule of Change in Fair Value of Level 3 Assets (Details) - U.S. Pension Plans [Member] - USD ($) $ in Millions	12 Months Ended
	May 31, 2017	May 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Balance at beginning of year	$ 23,017	$ 23,006
Actual return on plan assets:
Balance at end of year	24,933	23,017
Fair Value Inputs Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Balance at beginning of year	48
Actual return on plan assets:
Assets held during current year	5	2
Assets sold during the year	1
Purchases, sales and settlements	75	46
Balance at end of year	$ 129	$ 48