Retirement Plans (Details 1) - USD ($) $ in Millions	12 Months Ended
	May. 31, 2015	May. 31, 2014	May. 31, 2013	May. 31, 2012
Acturial gain/loss by component pre-tax [Abstract]
Discount rates	$ 791	$ 705	$ (1,076)
Return on assets	(35)	(1,013)	(696)
Demographic assumptions	1,434	$ 323	$ 404
Increase in overall projected benefit obligation	$ 1,200
U.S. pension plan actual rate of return on assets		13.30%	12.10%
Weighted Average Discount Rate Percent all pension postretirement plans	4.38%	4.57%	4.76%	4.44%
Total mark-to-market loss (gain)	$ 2,190	$ 15	$ (1,368)
Pension and Other Postretirement Benefit Expense [Abstract]
Defined benefit pension plans	(41)	99	163
Defined contribution plans	385	363	354
Postretirement healthcare plans	81	78	78
Retirement plans mark to market	2,190	15	(1,368)
Retirement plans costs	$ 2,615	$ 555	$ (773)