Retirement Plans - Schedule of Change in Fair Value of Level 3 Assets (Details) - Pension Plans [Member] - USD ($) $ in Millions	12 Months Ended
	May 31, 2020	May 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Balance at beginning of year	$ 24,898
Actual return on plan assets:
Balance at end of year	28,691	$ 24,898
U.S. Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Balance at beginning of year	23,320	22,057
Actual return on plan assets:
Balance at end of year	26,978	23,320
Fair Value Inputs Level 3 [Member] | U.S. Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Balance at beginning of year	302	209
Actual return on plan assets:
Assets held during current year	19	11
Assets sold during the year	16	13
Purchases, sales and settlements	79	69
Balance at end of year	$ 416	$ 302