Condensed Consolidated Statements of Changes in Common Stockholders' Investment - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Feb. 28, 2021	Feb. 29, 2020	Feb. 28, 2021	Feb. 29, 2020
Beginning Balance				$ 18,295
Net income		$ 892	$ 315	3,363	$ 1,620
Other comprehensive income, net of tax (expense)/benefit		134	(21)	383	(73)
Ending Balance		21,981	18,831	21,981	18,831
Common Stock
Beginning Balance		32	32	32	32
Ending Balance		32	32	32	32
Additional Paid-In Capital
Beginning Balance		3,400	3,287	3,356	3,231
Employee incentive plans and other		45	37	89	93
Ending Balance		3,445	3,324	3,445	3,324
Retained Earnings
Beginning Balance		27,208	25,431	25,216	24,648
Net income		892	315	3,363	1,620
Cash dividends declared		(173)	(170)	(686)	(679)
Employee incentive plans and other		(3)	(7)	31	(16)
Ending Balance		27,924	25,569	27,924	25,569
Retained Earnings | Cumulative Effect, Period of Adoption, Adjustment | Accounting Standards Update 2016-02 and 2018-02
Beginning Balance	[1]				(4)
Accumulated Other Comprehensive Income
Beginning Balance		(898)	(866)	(1,147)	(865)
Other comprehensive income, net of tax (expense)/benefit		134	(21)	383	(73)
Ending Balance		(764)	(887)	(764)	(887)
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		(8,703)	(9,225)	(9,162)	(9,289)
Purchase of treasury stock					(3)
Employee incentive plans and other		47	18	506	85
Ending Balance		$ (8,656)	$ (9,207)	$ (8,656)	$ (9,207)

[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.