Retirement Plans - Schedule of Change in Fair Value of Level 3 Assets (Details) - Pension Plans [Member] - USD ($) $ in Millions	12 Months Ended
	May 31, 2021	May 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Balance at beginning of year	$ 28,691
Actual return on plan assets:
Balance at end of year	31,918	$ 28,691
U.S. Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Balance at beginning of year	26,978	23,320
Actual return on plan assets:
Balance at end of year	29,785	26,978
Fair Value Inputs Level 3 [Member] | U.S. Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Balance at beginning of year	416	302
Actual return on plan assets:
Assets held during current year	41	19
Assets sold during the year	22	16
Purchases, sales and settlements	58	79
Balance at end of year	$ 537	$ 416