Common Stock and Stock-Based Compensation (Tables)

12 Months Ended

May 31, 2017

Share-based Compensation [Abstract]

Schedule of Compensation Cost for Share-based Payment Arrangements, Allocation of Share-based Compensation Costs by Plan

The following table summarizes the Company’s total stock-based compensation expense recognized in Operating overhead expense:

	Year Ended May 31,
(In millions)	2017		2016		2015
Stock options(1)	$	145	$	171	$	136
ESPPs	36		31		24
Restricted stock	34		34		31
TOTAL STOCK-BASED COMPENSATION EXPENSE	$	215	$	236	$	191

(1) Expense for stock options includes the expense associated with stock appreciation rights. Accelerated stock option expense is recorded for employees eligible for accelerated stock option vesting upon retirement. Accelerated stock option expense was $14 million, $30 million and $19 million for the years ended May 31, 2017, 2016 and 2015, respectively.

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions

The weighted average assumptions used to estimate these fair values are as follows:

	Year Ended May 31,
	2017		2016		2015
Dividend yield	1.1	%	1.0	%	1.2	%
Expected volatility	17.4	%	23.6	%	23.6	%
Weighted average expected life (in years)	6.0		5.8		5.8
Risk-free interest rate	1.3	%	1.7	%	1.7	%

Schedule of Share-based Compensation, Stock Options, Activity

The following summarizes the stock option transactions under the plan discussed above:

	Shares(1)		Weighted Average Option Price
	(In millions)
Options outstanding May 31, 2014	127.1		$	19.64
Exercised	(27.2	)	15.39
Forfeited	(2.1	)	29.51
Granted	18.4		38.84
Options outstanding May 31, 2015	116.2		23.50
Exercised	(22.5	)	17.75
Forfeited	(2.3	)	39.96
Granted	20.6		56.41
Options outstanding May 31, 2016	112.0		30.38
Exercised	(17.1	)	20.42
Forfeited	(2.3	)	49.47
Granted	12.2		57.81
Options outstanding May 31, 2017	104.8		$	34.79
Options exercisable at May 31,
2015	68.6		$	18.26
2016	66.5		21.48
2017	67.9		26.03

(1) Includes stock appreciation rights transactions.