Condensed Consolidated Statements of Changes in Common Stockholders' Investment - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Feb. 29, 2020	Feb. 28, 2019	Feb. 29, 2020	Feb. 28, 2019
Beginning Balance				$ 17,757
Net income		$ 315	$ 739	1,620	$ 2,509
Other comprehensive income, net of tax (expense)/benefit		(21)	80	(73)	(159)
Ending Balance		18,831	19,894	18,831	19,894
Common Stock
Beginning Balance		32	32	32	32
Ending Balance		32	32	32	32
Additional Paid-In Capital
Beginning Balance		3,287	3,185	3,231	3,117
Employee incentive plans and other		37	24	93	92
Ending Balance		3,324	3,209	3,324	3,209
Retained Earnings
Beginning Balance		25,431	26,080	24,648	24,823
Net income		315	739	1,620	2,509
Cash dividends declared		(170)	(169)	(679)	(683)
Employee incentive plans and other		(7)		(16)	1
Ending Balance		25,569	26,650	25,569	26,650
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		(866)	(817)	(865)	(578)
Other comprehensive income, net of tax (expense)/benefit		(21)	80	(73)	(159)
Ending Balance		(887)	(737)	(887)	(737)
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		(9,225)	(9,186)	(9,289)	(7,978)
Purchase of treasury stock			(93)	(3)	(1,365)
Employee incentive plans and other		18	19	85	83
Ending Balance		$ (9,207)	$ (9,260)	$ (9,207)	$ (9,260)

[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.