Retirement Plans (Details 2) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	May 31, 2016	May 31, 2015	May 31, 2016	May 31, 2015	May 31, 2014	May 31, 2013
Acturial gain/loss by component pre-tax [Abstract]
Actual versus expected return on assets			$ 1,285	$ (35)	$ (1,013)
Discount rate changes			1,129	791	705
Demographic assumption experience			(916)	1,434	323
Total mark-to-market loss	$ 1,500	$ 2,200	$ 1,498	2,190	$ 15
Increase in overall projected benefit obligation due to new mortality table.				$ 1,200
U.S. pension plan actual rate of return on assets			1.20%		13.30%
Weighted Average Discount Rate Percent all pension postretirement plans			4.04%	4.38%	4.57%	4.76%