Retirement Plans - Schedule of Change in Fair Value of Level 3 Assets (Details) - Pension Plans [Member] - USD ($) $ in Millions	12 Months Ended
	May 31, 2019	May 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Balance at beginning of year	$ 23,566
Actual return on plan assets:
Balance at end of year	24,898	$ 23,566
U.S. Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Balance at beginning of year	22,057	24,933
Actual return on plan assets:
Balance at end of year	23,320	22,057
Fair Value Inputs Level 3 [Member] | U.S. Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Balance at beginning of year	209	129
Actual return on plan assets:
Assets held during current year	11	8
Assets sold during the year	13	4
Purchases, sales and settlements	69	68
Balance at end of year	$ 302	$ 209