Condensed Consolidated Statements of Changes in Common Stockholders' Investment - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Nov. 30, 2019	Nov. 30, 2018	Nov. 30, 2019	Nov. 30, 2018
Beginning Balance				$ 17,757
Net income		$ 560	$ 935	1,305	$ 1,770
Other comprehensive income, net of tax (expense)/benefit		52	(54)	(52)	(239)
Ending Balance		18,659	19,294	18,659	19,294
Common Stock
Beginning Balance		32	32	32	32
Ending Balance		32	32	32	32
Additional Paid-In Capital
Beginning Balance		3,257	3,154	3,231	3,117
Employee incentive plans and other		30	31	56	68
Ending Balance		3,287	3,185	3,287	3,185
Retained Earnings
Beginning Balance		25,048	25,315	24,648	24,823
Net income		560	935	1,305	1,770
Cash dividends declared		(170)	(170)	(509)	(514)
Employee incentive plans and other		(7)		(9)	1
Ending Balance		25,431	26,080	25,431	26,080
Retained Earnings | Accounting Standards Update 2016-02 and 2018-02
Adoption of new accounting standards on June 1, 2019	[1]			(4)
Accumulated Other Comprehensive Income
Beginning Balance		(918)	(763)	(865)	(578)
Other comprehensive income, net of tax (expense)/benefit		52	(54)	(52)	(239)
Ending Balance		(866)	(817)	(866)	(817)
Accumulated Other Comprehensive Income | Accounting Standards Update 2018-02
Reclassification to retained earnings due to the adoption of a new accounting standard on June 1, 2019	[2]			51
Treasury Stock
Beginning Balance		(9,253)	(8,565)	(9,289)	(7,978)
Purchase of treasury stock			(646)	(3)	(1,271)
Employee incentive plans and other		28	25	67	63
Ending Balance		$ (9,225)	$ (9,186)	$ (9,225)	$ (9,186)

[1] Relates to the adoption of Accounting Standards Update (“ASU”) 2016-02 and ASU 2018-02.

[2] Relates to the adoption of ASU 2018-02.