Retirement Plans - Additional Information (Details) $ in Millions	1 Months Ended	12 Months Ended
	May 31, 2017 USD ($) Employee	May 31, 2018 USD ($)	May 31, 2017 USD ($)	May 31, 2016 USD ($)	May 31, 2015 USD ($)	May 31, 2014
Defined Benefit Plan Disclosure [Line Items]
U.S. pension plan actual rate of return on assets			9.60%	1.20%
Weighted average discount rate percent all pension postretirement plans			3.98%	4.04%	4.38%	4.57%
Increase in overall projected benefit obligation due to new mortality table.					$ 1,200
Actual rate of return on plan assets for the 15-year period			7.80%
Defined benefit plan health care cost trend rate assumed for next fiscal year			7.80%
Defined benefit plan ultimate health care cost trend rate			4.50%
Defined benefit plan year that rate reaches ultimate trend rate	2037		2037
U.S. Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected long-term rate of return on assets			6.50%	6.50%	7.75%
Number of former employees elected to receive lump sum distribution | Employee	18,300
Lump sum amount paid to former employees	$ 1,300
Defined benefit plan contributions by employer			$ 2,020	$ 693
U.S. Pension Plans [Member] | Scenario, Forecast [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan contributions by employer		$ 1,000
Defined benefit pension plan, required employer contribution		$ 700
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected long-term rate of return on assets			6.50%	6.50%	7.75%